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<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="Asciidoctor 2.0.26"><meta name="description" content="PCRE2's native API"><title>pcre2api(3)</title><link rel="stylesheet" href="./css/document.css"><link rel="stylesheet" href="./css/standalone.css"><meta name="color-scheme" content="light dark"><meta name="theme-color" media="(prefers-color-scheme: light)" content="#0085cc"><meta name="theme-color" media="(prefers-color-scheme: dark)" content="#33b8ff"></head><body class="manpage toc2 toc-right offline-manual"><header class="offline-nav"><nav><a class="offline-index" href="./index.html">Index</a><a class="offline-home" href="https://www.pcre2.org/"><span aria-hidden="true">🌐︎</span> PCRE2 homepage</a></nav></header><main class="document-page"><header class="document-title"><h1>pcre2api(3)</h1><p class="document-meta">PCRE2 10.50-DEV manual; updated <time datetime="2025-12-08">8 Dec 2025</time></p></header><div class="document-layout"><nav id="toc" class="toc2" role="doc-toc"><h2 id="toc-title">Contents</h2><ol class="toc-list level-1"><li><a href="#_description" title="Description">Description</a></li><li><a href="#_pcre2_native_api_basic_functions" title="PCRE2 native API basic functions">PCRE2 native API basic functions</a></li><li><a href="#_pcre2_native_api_auxiliary_match_functions" title="PCRE2 native API auxiliary match functions">PCRE2 native API auxiliary match functions</a></li><li><a href="#_pcre2_native_api_general_context_functions" title="PCRE2 native API general context functions">PCRE2 native API general context functions</a></li><li><a href="#_pcre2_native_api_compile_context_functions" title="PCRE2 native API compile context functions">PCRE2 native API compile context functions</a></li><li><a href="#_pcre2_native_api_match_context_functions" title="PCRE2 native API match context functions">PCRE2 native API match context functions</a></li><li><a href="#_pcre2_native_api_string_extraction_functions" title="PCRE2 native API string extraction functions">PCRE2 native API string extraction functions</a></li><li><a href="#_pcre2_native_api_string_substitution_function" title="PCRE2 native API string substitution function">PCRE2 native API string substitution function</a></li><li><a href="#_pcre2_native_api_jit_functions" title="PCRE2 native API JIT functions">PCRE2 native API JIT functions</a></li><li><a href="#_pcre2_native_api_serialization_functions" title="PCRE2 native API serialization functions">PCRE2 native API serialization functions</a></li><li><a href="#_pcre2_native_api_auxiliary_functions" title="PCRE2 native API auxiliary functions">PCRE2 native API auxiliary functions</a></li><li><a href="#_pcre2_native_api_obsolete_functions" title="PCRE2 native API obsolete functions">PCRE2 native API obsolete functions</a></li><li><a href="#_pcre2_experimental_pattern_conversion_functions" title="PCRE2 experimental pattern conversion functions">PCRE2 experimental pattern conversion functions</a></li><li><a href="#_pcre2_8_bit_16_bit_and_32_bit_libraries" title="PCRE2 8-bit, 16-bit, and 32-bit libraries">PCRE2 8-bit, 16-bit, and 32-bit libraries</a></li><li><a href="#_pcre2_api_overview" title="PCRE2 API overview">PCRE2 API overview</a></li><li><a href="#_string_lengths_and_offsets" title="String lengths and offsets">String lengths and offsets</a></li><li><a href="#_newlines" title="Newlines">Newlines</a></li><li><a href="#_multithreading" title="Multithreading">Multithreading</a><ol class="toc-list level-2"><li><a href="#_the_compiled_pattern" title="The compiled pattern">The compiled pattern</a></li><li><a href="#_context_blocks" title="Context blocks">Context blocks</a></li><li><a href="#_match_blocks" title="Match blocks">Match blocks</a></li></ol></li><li><a href="#pcre2-contexts" title="PCRE2 contexts">PCRE2 contexts</a><ol class="toc-list level-2"><li><a href="#_the_general_context" title="The general context">The general context</a></li><li><a href="#_the_compile_context" title="The compile context">The compile context</a></li><li><a href="#match-context" title="The match context">The match context</a></li></ol></li><li><a href="#_checking_build_time_options" title="Checking build-time options">Checking build-time options</a></li><li><a href="#compiling-a-pattern" title="Compiling a pattern">Compiling a pattern</a><ol class="toc-list level-2"><li><a href="#_main_compile_options" title="Main compile options">Main compile options</a></li><li><a href="#extra-compile-options" title="Extra compile options">Extra compile options</a></li></ol></li><li><a href="#_just_in_time_jit_compilation" title="Just-in-time (JIT) compilation">Just-in-time (JIT) compilation</a></li><li><a href="#locale-support" title="Locale support">Locale support</a><ol class="toc-list level-2"><li><a href="#_saving_locale_tables" title="Saving locale tables">Saving locale tables</a></li></ol></li><li><a href="#information-about-compiled-pattern" title="Information about a compiled pattern">Information about a compiled pattern</a></li><li><a href="#information-about-pattern-callouts" title="Information about a pattern’s callouts">Information about a pattern’s callouts</a></li><li><a href="#_serialization_and_precompiling" title="Serialization and precompiling">Serialization and precompiling</a></li><li><a href="#_the_match_data_block" title="The match data block">The match data block</a></li><li><a href="#_memory_use_for_match_data_blocks" title="Memory use for match data blocks">Memory use for match data blocks</a></li><li><a href="#_matching_a_pattern_the_traditional_function" title="Matching a pattern: the traditional function">Matching a pattern: the traditional function</a><ol class="toc-list level-2"><li><a href="#_the_string_to_be_matched_by_pcre2_match" title="The string to be matched by pcre2_match()">The string to be matched by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code></a></li><li><a href="#match-option-bits" title="Option bits for pcre2_match()">Option bits for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code></a></li></ol></li><li><a href="#_newline_handling_when_matching" title="Newline handling when matching">Newline handling when matching</a></li><li><a href="#matched-strings" title="How pcre2_match() returns a string and captured substrings">How <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> returns a string and captured substrings</a></li><li><a href="#other-match-information" title="Other information about a match">Other information about a match</a></li><li><a href="#_error_returns_from_pcre2_match" title="Error returns from pcre2_match()">Error returns from <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code></a></li><li><a href="#_obtaining_a_textual_error_message" title="Obtaining a textual error message">Obtaining a textual error message</a></li><li><a href="#iterating-over-matches" title="Iterating over all matches">Iterating over all matches</a></li><li><a href="#_extracting_captured_substrings_by_number" title="Extracting captured substrings by number">Extracting captured substrings by number</a></li><li><a href="#extracting-substrings-by-name" title="Extracting a list of all captured substrings">Extracting a list of all captured substrings</a></li><li><a href="#_extracting_captured_substrings_by_name" title="Extracting captured substrings by name">Extracting captured substrings by name</a></li><li><a href="#creating-substitution-string" title="Creating a new string with substitutions">Creating a new string with substitutions</a><ol class="toc-list level-2"><li><a href="#_substitution_errors" title="Substitution errors">Substitution errors</a></li><li><a href="#_substitution_callouts" title="Substitution callouts">Substitution callouts</a></li><li><a href="#_substitution_case_callouts" title="Substitution case callouts">Substitution case callouts</a></li></ol></li><li><a href="#_duplicate_capture_group_names" title="Duplicate capture group names">Duplicate capture group names</a></li><li><a href="#_finding_all_possible_matches_at_one_position" title="Finding all possible matches at one position">Finding all possible matches at one position</a></li><li><a href="#_matching_a_pattern_the_alternative_function" title="Matching a pattern: the alternative function">Matching a pattern: the alternative function</a><ol class="toc-list level-2"><li><a href="#_option_bits_for_pcre2_dfa_match" title="Option bits for pcre2_dfa_match()">Option bits for <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code></a></li><li><a href="#_successful_returns_from_pcre2_dfa_match" title="Successful returns from pcre2_dfa_match()">Successful returns from <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code></a></li><li><a href="#_error_returns_from_pcre2_dfa_match" title="Error returns from pcre2_dfa_match()">Error returns from <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code></a></li></ol></li><li><a href="#_see_also" title="See also">See also</a></li></ol></nav><article class="prose" id="content"><section class="doc-section level-1"><h2 id="_description">Description</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="cp">#include</span> <span class="cpf">&lt;pcre2.h&gt;</span></code></pre></div>
<p>PCRE2 is a new API for PCRE, starting at release 10.0. This document contains a
description of all its native functions. See the
<a href="./pcre2.html"><code>pcre2</code></a>
document for an overview of all the PCRE2 documentation.</p></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_basic_functions">PCRE2 native API basic functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_code</span> <span class="p">*</span><span class="nf">pcre2_compile</span><span class="p">(</span><span class="kt">PCRE2_SPTR</span> <span class="nv">pattern</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">patlen</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">int</span> <span class="p">*</span><span class="nv">errorptr</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">erroroffset</span><span class="p">,</span>
<span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_code_free</span><span class="p">(</span><span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">);</span>
<span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nf">pcre2_match_data_create</span><span class="p">(</span>
<span class="kt">uint32_t</span> <span class="nv">oveccount</span><span class="p">,</span> <span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nf">pcre2_match_data_create_from_pattern</span><span class="p">(</span>
<span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_match</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">PCRE2_SPTR</span> <span class="nv">subject</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">start_offset</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_dfa_match</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">PCRE2_SPTR</span> <span class="nv">subject</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">start_offset</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span> <span class="kt">int</span> <span class="p">*</span><span class="nv">workspace</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">wscount</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_match_data_free</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_auxiliary_match_functions">PCRE2 native API auxiliary match functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">PCRE2_SPTR</span> <span class="nf">pcre2_get_mark</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">PCRE2_SIZE</span> <span class="nf">pcre2_get_match_data_size</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">PCRE2_SIZE</span> <span class="nf">pcre2_get_match_data_heapframes_size</span><span class="p">(</span>
<span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">uint32_t</span> <span class="nf">pcre2_get_ovector_count</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nf">pcre2_get_ovector_pointer</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">PCRE2_SIZE</span> <span class="nf">pcre2_get_startchar</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">PCRE2_SPTR</span> <span class="nf">pcre2_get_subject</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">lengthptr</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_general_context_functions">PCRE2 native API general context functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nf">pcre2_general_context_create</span><span class="p">(</span>
<span class="kt">void</span> <span class="p">*</span><span class="p">(</span><span class="p">*</span><span class="nv">private_malloc</span><span class="p">)(</span><span class="kt">size_t</span> <span class="nv">size</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">memory_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">(</span><span class="p">*</span><span class="nv">private_free</span><span class="p">)(</span><span class="kt">void</span> <span class="p">*</span><span class="nv">ptr</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">memory_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">memory_data</span><span class="p">);</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nf">pcre2_general_context_copy</span><span class="p">(</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_general_context_free</span><span class="p">(</span><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_compile_context_functions">PCRE2 native API compile context functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nf">pcre2_compile_context_create</span><span class="p">(</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nf">pcre2_compile_context_copy</span><span class="p">(</span>
<span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_compile_context_free</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_bsr</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span> <span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">value</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_max_pattern_length</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">length</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_newline</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">newline</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_parens_nest_limit</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_bsr</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span> <span class="kt">uint32_t</span> <span class="nv">value</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_character_tables</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">const</span> <span class="kt">uint8_t</span> <span class="p">*</span><span class="nv">tables</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_compile_extra_options</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_max_pattern_length</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_max_pattern_compiled_length</span><span class="p">(</span>
<span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_max_varlookbehind</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_newline</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">newline</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_parens_nest_limit</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_compile_recursion_guard</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">int</span> <span class="p">(</span><span class="p">*</span><span class="nv">guard</span><span class="p">)(</span><span class="kt">uint32_t</span> <span class="nv">depth</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">user_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">user_data</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_optimize</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">directive</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_match_context_functions">PCRE2 native API match context functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nf">pcre2_match_context_create</span><span class="p">(</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nf">pcre2_match_context_copy</span><span class="p">(</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_match_context_free</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_heap_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_match_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_depth_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_offset_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_callout</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">int</span> <span class="p">(</span><span class="p">*</span><span class="nv">callout</span><span class="p">)(</span>
<span class="kt">pcre2_callout_block</span> <span class="p">*</span><span class="nv">callout_block</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callout_data</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_substitute_callout</span><span class="p">(</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">int</span> <span class="p">(</span><span class="p">*</span><span class="nv">substitute_callout</span><span class="p">)(</span>
<span class="kt">pcre2_substitute_callout_block</span> <span class="p">*</span><span class="nv">callout_block</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_callout_data</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_substitute_case_callout</span><span class="p">(</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="nf">PCRE2_SIZE</span> <span class="p">(</span><span class="p">*</span><span class="nv">substitute_case_callout</span><span class="p">)(</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">input</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">input_length</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">output</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">output_capacity</span><span class="p">,</span>
<span class="kt">int</span> <span class="nv">case_operation</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_case_callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_case_callout_data</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_offset_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_heap_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_match_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_depth_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_string_extraction_functions">PCRE2 native API string extraction functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_substring_copy_byname</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">buffer</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_copy_bynumber</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">stringnumber</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">buffer</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_substring_free</span><span class="p">(</span><span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">string</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_get_byname</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="p">*</span><span class="nv">stringptr</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_get_bynumber</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">stringnumber</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="p">*</span><span class="nv">stringptr</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_length_byname</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_length_bynumber</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">stringnumber</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_nametable_scan</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="p">*</span><span class="nv">firstptr</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="p">*</span><span class="nv">lastptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_number_from_name</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_substring_list_free</span><span class="p">(</span><span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="p">*</span><span class="nv">list</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_list_get</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="p">*</span><span class="p">*</span><span class="nv">listptr</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="p">*</span><span class="nv">lengthsptr</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_string_substitution_function">PCRE2 native API string substitution function</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_substitute</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">PCRE2_SPTR</span> <span class="nv">subject</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">start_offset</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">replacement</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">rlength</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">buffer</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">blength</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_jit_functions">PCRE2 native API JIT functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_jit_compile</span><span class="p">(</span><span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_jit_match</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">PCRE2_SPTR</span> <span class="nv">subject</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">start_offset</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_jit_free_unused_memory</span><span class="p">(</span><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">pcre2_jit_stack</span> <span class="p">*</span><span class="nf">pcre2_jit_stack_create</span><span class="p">(</span>
<span class="kt">size_t</span> <span class="nv">startsize</span><span class="p">,</span> <span class="kt">size_t</span> <span class="nv">maxsize</span><span class="p">,</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_jit_stack_assign</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">pcre2_jit_callback</span> <span class="nv">callback</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callback_data</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_jit_stack_free</span><span class="p">(</span><span class="kt">pcre2_jit_stack</span> <span class="p">*</span><span class="nv">jit_stack</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_serialization_functions">PCRE2 native API serialization functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int32_t</span> <span class="nf">pcre2_serialize_decode</span><span class="p">(</span><span class="kt">pcre2_code</span> <span class="p">*</span><span class="p">*</span><span class="nv">codes</span><span class="p">,</span>
<span class="kt">int32_t</span> <span class="nv">number_of_codes</span><span class="p">,</span>
<span class="kt">const</span> <span class="kt">uint8_t</span> <span class="p">*</span><span class="nv">bytes</span><span class="p">,</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">int32_t</span> <span class="nf">pcre2_serialize_encode</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="p">*</span><span class="nv">codes</span><span class="p">,</span>
<span class="kt">int32_t</span> <span class="nv">number_of_codes</span><span class="p">,</span>
<span class="kt">uint8_t</span> <span class="p">*</span><span class="p">*</span><span class="nv">serialized_bytes</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">serialized_size</span><span class="p">,</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_serialize_free</span><span class="p">(</span><span class="kt">uint8_t</span> <span class="p">*</span><span class="nv">bytes</span><span class="p">);</span>
<span class="kt">int32_t</span> <span class="nf">pcre2_serialize_get_number_of_codes</span><span class="p">(</span><span class="kt">const</span> <span class="kt">uint8_t</span> <span class="p">*</span><span class="nv">bytes</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_auxiliary_functions">PCRE2 native API auxiliary functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_code</span> <span class="p">*</span><span class="nf">pcre2_code_copy</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">);</span>
<span class="kt">pcre2_code</span> <span class="p">*</span><span class="nf">pcre2_code_copy_with_tables</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_error_message</span><span class="p">(</span><span class="kt">int</span> <span class="nv">errorcode</span><span class="p">,</span> <span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">buffer</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">bufflen</span><span class="p">);</span>
<span class="kt">const</span> <span class="kt">uint8_t</span> <span class="p">*</span><span class="nf">pcre2_maketables</span><span class="p">(</span><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_maketables_free</span><span class="p">(</span><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">,</span>
<span class="kt">const</span> <span class="kt">uint8_t</span> <span class="p">*</span><span class="nv">tables</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_pattern_info</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">uint32_t</span> <span class="nv">what</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">where</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_callout_enumerate</span><span class="p">(</span>
<span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span>
<span class="kt">int</span> <span class="p">(</span><span class="p">*</span><span class="nv">callback</span><span class="p">)(</span><span class="kt">pcre2_callout_enumerate_block</span> <span class="p">*</span><span class="nv">callout_block</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callout_data</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_config</span><span class="p">(</span><span class="kt">uint32_t</span> <span class="nv">what</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">where</span><span class="p">);</span></code></pre></div></section>
<section class="doc-section level-1"><h2 id="_pcre2_native_api_obsolete_functions">PCRE2 native API obsolete functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_recursion_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_recursion_memory_management</span><span class="p">(</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="p">(</span><span class="p">*</span><span class="nv">mymalloc</span><span class="p">)(</span><span class="kt">size_t</span> <span class="nv">size</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">mydata</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">(</span><span class="p">*</span><span class="nv">myfree</span><span class="p">)(</span><span class="kt">void</span> <span class="p">*</span><span class="nv">ptr</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">mydata</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">mydata</span><span class="p">);</span></code></pre></div>
<p>These functions became obsolete at release 10.30 and are retained only for
backward compatibility. They should not be used in new code. The first is
replaced by <code class="function pcre2-api rouge"><span class="nf">pcre2_set_depth_limit()</span></code>; the second is no longer needed and
has no effect (it always returns zero).</p></section>
<section class="doc-section level-1"><h2 id="_pcre2_experimental_pattern_conversion_functions">PCRE2 experimental pattern conversion functions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_convert_context</span> <span class="p">*</span><span class="nf">pcre2_convert_context_create</span><span class="p">(</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">pcre2_convert_context</span> <span class="p">*</span><span class="nf">pcre2_convert_context_copy</span><span class="p">(</span>
<span class="kt">pcre2_convert_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_convert_context_free</span><span class="p">(</span><span class="kt">pcre2_convert_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_glob_escape</span><span class="p">(</span><span class="kt">pcre2_convert_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">escape_char</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_set_glob_separator</span><span class="p">(</span><span class="kt">pcre2_convert_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">separator_char</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_pattern_convert</span><span class="p">(</span><span class="kt">PCRE2_SPTR</span> <span class="nv">pattern</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">plength</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="p">*</span><span class="nv">buffptr</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">bufflenptr</span><span class="p">,</span>
<span class="kt">pcre2_convert_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_converted_pattern_free</span><span class="p">(</span><span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">converted</span><span class="p">);</span></code></pre></div>
<p>These functions provide a way of converting non-PCRE2 patterns into
patterns that can be processed by <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>. This facility is
experimental and may be changed in future releases. At present, "globs" and
POSIX basic and extended patterns can be converted. Details are given in the
<a href="./pcre2convert.html"><code>pcre2convert</code></a>
documentation.</p></section>
<section class="doc-section level-1"><h2 id="_pcre2_8_bit_16_bit_and_32_bit_libraries">PCRE2 8-bit, 16-bit, and 32-bit libraries</h2><p>There are three PCRE2 libraries, supporting 8-bit, 16-bit, and 32-bit code
units, respectively. However, there is just one header file, <code>pcre2.h</code>.
This contains the function prototypes and other definitions for all three
libraries. One, two, or all three can be installed simultaneously. On Unix-like
systems the libraries are called <code>libpcre2-8</code>, <code>libpcre2-16</code>, and
<code>libpcre2-32</code>, and they can also co-exist with the original PCRE libraries.
Every PCRE2 function comes in three different forms, one for each library, for
example:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="nf">pcre2_compile_8</span><span class="p">()</span>
<span class="nf">pcre2_compile_16</span><span class="p">()</span>
<span class="nf">pcre2_compile_32</span><span class="p">()</span></code></pre></div>
<p>There are also three different sets of data types:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="kt">PCRE2_UCHAR8</span><span class="p">,</span> <span class="kt">PCRE2_UCHAR16</span><span class="p">,</span> <span class="kt">PCRE2_UCHAR32</span>
<span class="kt">PCRE2_SPTR8</span><span class="p">,</span> <span class="kt">PCRE2_SPTR16</span><span class="p">,</span> <span class="kt">PCRE2_SPTR32</span></code></pre></div>
<p>The UCHAR types define unsigned code units of the appropriate widths.
For example, <code class="type pcre2-api rouge"><span class="kt">PCRE2_UCHAR16</span></code> is usually defined as <code class="type pcre2-api rouge"><span class="kt">uint16_t</span></code>.
The SPTR types are pointers to constants of the equivalent UCHAR types,
that is, they are pointers to vectors of unsigned code units.</p>
<p>Character strings are passed to a PCRE2 library as sequences of unsigned
integers in code units of the appropriate width. The length of a string may
be given as a number of code units, or the string may be specified as
zero-terminated.</p>
<p>Many applications use only one code unit width. For their convenience, macros
are defined whose names are the generic forms such as <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> and
<code class="type pcre2-api rouge"><span class="kt">PCRE2_SPTR</span></code>. These macros use the value of the macro <code class="constant pcre2-api rouge"><span class="no">PCRE2_CODE_UNIT_WIDTH</span></code> to
generate the appropriate width-specific function and macro names.
<code class="constant pcre2-api rouge"><span class="no">PCRE2_CODE_UNIT_WIDTH</span></code> is not defined by default. An application must define it
to be 8, 16, or 32 before including <code>pcre2.h</code> in order to make use of the
generic names.</p>
<p>Applications that use more than one code unit width can be linked with more
than one PCRE2 library, but must define <code class="constant pcre2-api rouge"><span class="no">PCRE2_CODE_UNIT_WIDTH</span></code> to be 0 before
including <code>pcre2.h</code>, and then use the real function names. Any code that is
to be included in an environment where the value of <code class="constant pcre2-api rouge"><span class="no">PCRE2_CODE_UNIT_WIDTH</span></code> is
unknown should also use the real function names. (Unfortunately, it is not
possible in C code to save and restore the value of a macro.)</p>
<p>If <code class="constant pcre2-api rouge"><span class="no">PCRE2_CODE_UNIT_WIDTH</span></code> is not defined before including <code>pcre2.h</code>, a
compiler error occurs.</p>
<p>When using multiple libraries in an application, you must take care when
processing any particular pattern to use only functions from a single library.
For example, if you want to run a match using a pattern that was compiled with
<code class="c rouge" data-lang="c"><span class="nf">pcre2_compile_16</span><span class="p">()</span></code>, you must do so with <code class="c rouge" data-lang="c"><span class="nf">pcre2_match_16</span><span class="p">()</span></code>, not
<code class="c rouge" data-lang="c"><span class="nf">pcre2_match_8</span><span class="p">()</span></code> or <code class="c rouge" data-lang="c"><span class="nf">pcre2_match_32</span><span class="p">()</span></code>.</p>
<p>In the function summaries above, and in the rest of this document and other
PCRE2 documents, functions and data types are described using their generic
names, without the <code>_8</code>, <code>_16</code>, or <code>_32</code> suffix.</p></section>
<section class="doc-section level-1"><h2 id="_pcre2_api_overview">PCRE2 API overview</h2><p>PCRE2 has its own native API, which is described in this document. There are
also some wrapper functions for the 8-bit library that correspond to the
POSIX regular expression API, but they do not give access to all the
functionality of PCRE2 and they are not thread-safe. They are described in the
<a href="./pcre2posix.html"><code>pcre2posix</code></a>
documentation. Both these APIs define a set of C function calls.</p>
<p>The native API C data types, function prototypes, option values, and error
codes are defined in the header file <code>pcre2.h</code>, which also contains
definitions of <code class="constant pcre2-api rouge"><span class="no">PCRE2_MAJOR</span></code> and <code class="constant pcre2-api rouge"><span class="no">PCRE2_MINOR</span></code>, the major and minor release numbers
for the library. Applications can use these to include support for different
releases of PCRE2.</p>
<p>In a Windows environment, if you want to statically link an application program
against a non-dll PCRE2 library, you must define <code class="constant pcre2-api rouge"><span class="no">PCRE2_STATIC</span></code> before including
<code>pcre2.h</code>.</p>
<p>The functions <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> and <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> are used for
compiling and matching regular expressions in a Perl-compatible manner. A
sample program that demonstrates the simplest way of using them is provided in
the file called <code>pcre2demo.c</code> in the PCRE2 source distribution. A listing
of this program is given in the
<a href="./pcre2demo.html"><code>pcre2demo</code></a>
documentation, and the
<a href="./pcre2sample.html"><code>pcre2sample</code></a>
documentation describes how to compile and run it.</p>
<p>The compiling and matching functions recognize various options that are passed
as bits in an options argument. There are also some more complicated parameters
such as custom memory management functions and resource limits that are passed
in "contexts" (which are just memory blocks, described below). Simple
applications do not need to make use of contexts.</p>
<p>Just-in-time (JIT) compiler support is an optional feature of PCRE2 that can be
built in appropriate hardware environments. It greatly speeds up the matching
performance of many patterns. Programs can request that it be used if
available by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_jit_compile()</span></code> after a pattern has been
successfully compiled by <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>. This does nothing if JIT
support is not available.</p>
<p>More complicated programs might need to make use of the specialist functions
<code class="function pcre2-api rouge"><span class="nf">pcre2_jit_stack_create()</span></code>, <code class="function pcre2-api rouge"><span class="nf">pcre2_jit_stack_free()</span></code>, and
<code class="function pcre2-api rouge"><span class="nf">pcre2_jit_stack_assign()</span></code> in order to control the JIT code’s memory usage.</p>
<p>JIT matching is automatically used by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> if it is available,
unless the <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_JIT</span></code> option is set. There is also a direct interface for JIT
matching, which gives improved performance at the expense of less sanity
checking. The JIT-specific functions are discussed in the
<a href="./pcre2jit.html"><code>pcre2jit</code></a>
documentation.</p>
<p>A second matching function, <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, which is not
Perl-compatible, is also provided. This uses a different algorithm for the
matching. The alternative algorithm finds all possible matches (at a given
point in the subject), and scans the subject just once (unless there are
lookaround assertions). However, this algorithm does not return captured
substrings. A description of the two matching algorithms and their advantages
and disadvantages is given in the
<a href="./pcre2matching.html"><code>pcre2matching</code></a>
documentation. There is no JIT support for <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>.</p>
<p>In addition to the main compiling and matching functions, there are convenience
functions for extracting captured substrings from a subject string that has
been matched by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>. They are:</p>
<ul class="compact"><li><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_copy_byname()</span></code></li><li><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_copy_bynumber()</span></code></li><li><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_get_byname()</span></code></li><li><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_get_bynumber()</span></code></li><li><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_list_get()</span></code></li><li><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_length_byname()</span></code></li><li><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_length_bynumber()</span></code></li><li><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_nametable_scan()</span></code></li><li><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_number_from_name()</span></code></li></ul>
<p><code class="function pcre2-api rouge"><span class="nf">pcre2_substring_free()</span></code> and <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_list_free()</span></code> are also
provided, to free memory used for extracted strings. If either of these
functions is called with a <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> argument, the function returns immediately
without doing anything.</p>
<p>The function <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> can be called to match a pattern and
return a copy of the subject string with substitutions for parts that were
matched.</p>
<p>Functions whose names begin with <code class="c rouge" data-lang="c"><span class="kt">pcre2_serialize_</span></code> are used for saving
compiled patterns on disc or elsewhere, and reloading them later.</p>
<p>Finally, there are functions for finding out information about a compiled
pattern (<code class="function pcre2-api rouge"><span class="nf">pcre2_pattern_info()</span></code>) and about the configuration with which
PCRE2 was built (<code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code>) and that it is using.</p>
<p>Functions with names ending with <code class="c rouge" data-lang="c"><span class="nf">_free</span><span class="p">()</span></code> are used for freeing memory
blocks of various sorts. In all cases, if one of these functions is called with
a <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> argument, it does nothing.</p></section>
<section class="doc-section level-1"><h2 id="_string_lengths_and_offsets">String lengths and offsets</h2><p>The PCRE2 API uses string lengths and offsets into strings of code units in
several places. These values are always of type <code class="type pcre2-api rouge"><span class="kt">PCRE2_SIZE</span></code>, which is an
unsigned integer type, currently always defined as <code class="type pcre2-api rouge"><span class="kt">size_t</span></code>. The largest
value that can be stored in such a type (that is <code class="c rouge" data-lang="c"><span class="o">~</span><span class="p">(</span><span class="kt">PCRE2_SIZE</span><span class="p">)</span><span class="mi">0</span></code>) is reserved
as a special indicator for zero-terminated strings and unset offsets.
Therefore, the longest string that can be handled is one less than this
maximum. Note that string lengths are always given in code units. Only in the
8-bit library is such a length the same as the number of bytes in the string.</p></section>
<section class="doc-section level-1"><h2 id="_newlines">Newlines</h2><p>PCRE2 supports five different conventions for indicating line breaks in
strings: a single CR (carriage return) character, a single LF (linefeed)
character, the two-character sequence CRLF, any of the three preceding, or any
Unicode newline sequence. The Unicode newline sequences are the three just
mentioned, plus the single characters VT (vertical tab, <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-1"><code class="character pcre2-api rouge"><span class="sc">U+000B</span></code><span class="character-card" id="pcre2-character-1" role="tooltip" aria-label="LINE TABULATION (U+000B)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="LINE TABULATION"></span><span class="character-codepoint" data-codepoint="U+000B"></span></span></span>), FF (form feed,
<span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-2"><code class="character pcre2-api rouge"><span class="sc">U+000C</span></code><span class="character-card" id="pcre2-character-2" role="tooltip" aria-label="FORM FEED (U+000C)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="FORM FEED"></span><span class="character-codepoint" data-codepoint="U+000C"></span></span></span>), NEL (next line, <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-3"><code class="character pcre2-api rouge"><span class="sc">U+0085</span></code><span class="character-card" id="pcre2-character-3" role="tooltip" aria-label="NEXT LINE (U+0085)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="NEXT LINE"></span><span class="character-codepoint" data-codepoint="U+0085"></span></span></span>), LS (line separator, <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-4"><code class="character pcre2-api rouge"><span class="sc">U+2028</span></code><span class="character-card" id="pcre2-character-4" role="tooltip" aria-label="LINE SEPARATOR (U+2028)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="LINE SEPARATOR"></span><span class="character-codepoint" data-codepoint="U+2028"></span></span></span>), and PS
(paragraph separator, <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-5"><code class="character pcre2-api rouge"><span class="sc">U+2029</span></code><span class="character-card" id="pcre2-character-5" role="tooltip" aria-label="PARAGRAPH SEPARATOR (U+2029)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="PARAGRAPH SEPARATOR"></span><span class="character-codepoint" data-codepoint="U+2029"></span></span></span>).</p>
<p>Each of the first three conventions is used by at least one operating system as
its standard newline sequence. When PCRE2 is built, a default can be specified.
If it is not, the default is set to LF, which is the Unix standard. However,
the newline convention can be changed by an application when calling
<code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>, or it can be specified by special text at the start of
the pattern itself; this overrides any other settings. See the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
page for details of the special character sequences.</p>
<p>In the PCRE2 documentation the word "newline" is used to mean "the character or
pair of characters that indicate a line break". The choice of newline
convention affects the handling of the dot, circumflex, and dollar
metacharacters, the handling of <code class="regex rouge"><span class="pcre2-semantic">#</span></code>-comments in <code class="regex rouge"><span class="pcre2-semantic">/x</span></code> mode, and, when CRLF is a
recognized line ending sequence, the match position advancement for a
non-anchored pattern. There is more detail about this in the
section <a href="#match-option-bits">Option bits for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code></a>
below.</p>
<p>The choice of newline convention does not affect the interpretation of
the <code class="regex rouge"><span class="pcre2-semantic">\n</span></code> or <code class="regex rouge"><span class="pcre2-semantic">\r</span></code> escape sequences, nor does it affect what <code class="regex rouge"><span class="pcre2-semantic">\R</span></code> matches; this has
its own separate convention.</p></section>
<section class="doc-section level-1"><h2 id="_multithreading">Multithreading</h2><p>In a multithreaded application it is important to keep thread-specific data
separate from data that can be shared between threads. The PCRE2 library code
itself is thread-safe: it contains no static or global variables. The API is
designed to be fairly simple for non-threaded applications while at the same
time ensuring that multithreaded applications can use it.</p>
<p>There are several different blocks of data that are used to pass information
between the application and the PCRE2 libraries.</p>
<section class="doc-section level-2"><h3 id="_the_compiled_pattern">The compiled pattern</h3><p>A pointer to the compiled form of a pattern is returned to the user when
<code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> is successful. The data in the compiled pattern is fixed,
and does not change when the pattern is matched. Therefore, it is thread-safe,
that is, the same compiled pattern can be used by more than one thread
simultaneously. For example, an application can compile all its patterns at the
start, before forking off multiple threads that use them. However, if the
just-in-time (JIT) optimization feature is being used, it needs separate memory
stack areas for each thread. See the
<a href="./pcre2jit.html"><code>pcre2jit</code></a>
documentation for more details.</p>
<p>In a more complicated situation, where patterns are compiled only when they are
first needed, but are still shared between threads, pointers to compiled
patterns must be protected from simultaneous writing by multiple threads. This
is somewhat tricky to do correctly. If you know that writing to a pointer is
atomic in your environment, you can use logic like this:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="c1">// Get a read-only (shared) lock (mutex) for pointer</span>
<span class="k">if</span> <span class="p">(</span><span class="nv">pointer</span> <span class="o">==</span> <span class="kc">NULL</span><span class="p">)</span>
<span class="p">{</span>
<span class="c1">// Get a write (unique) lock for pointer</span>
<span class="k">if</span> <span class="p">(</span><span class="nv">pointer</span> <span class="o">==</span> <span class="kc">NULL</span><span class="p">)</span>
<span class="nv">pointer</span> <span class="o">=</span> <span class="nf">pcre2_compile</span><span class="p">(...);</span>
<span class="p">}</span>
<span class="c1">// Release the lock</span>
<span class="c1">// Use pointer in pcre2_match()</span></code></pre></div>
<p>Of course, testing for compilation errors should also be included in the code.</p>
<p>The reason for checking the pointer a second time is as follows: Several
threads may have acquired the shared lock and tested the pointer for being
<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, but only one of them will be given the write lock, with the rest kept
waiting. The winning thread will compile the pattern and store the result.
After this thread releases the write lock, another thread will get it, and if
it does not retest pointer for being <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, will recompile the pattern and
overwrite the pointer, creating a memory leak and possibly causing other
issues.</p>
<p>In an environment where writing to a pointer may not be atomic, the above logic
is not sufficient. The thread that is doing the compiling may be descheduled
after writing only part of the pointer, which could cause other threads to use
an invalid value. Instead of checking the pointer itself, a separate "pointer
is valid" flag (that can be updated atomically) must be used:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="c1">// Get a read-only (shared) lock (mutex) for pointer</span>
<span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="nv">pointer_is_valid</span><span class="p">)</span>
<span class="p">{</span>
<span class="c1">// Get a write (unique) lock for pointer</span>
<span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="nv">pointer_is_valid</span><span class="p">)</span>
<span class="p">{</span>
<span class="nv">pointer</span> <span class="o">=</span> <span class="nf">pcre2_compile</span><span class="p">(...);</span>
<span class="nv">pointer_is_valid</span> <span class="o">=</span> <span class="kc">TRUE</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="c1">// Release the lock</span>
<span class="c1">// Use pointer in pcre2_match()</span></code></pre></div>
<p>If JIT is being used, but the JIT compilation is not being done immediately
(perhaps waiting to see if the pattern is used often enough), similar logic is
required. JIT compilation updates a value within the compiled code block, so a
thread must gain unique write access to the pointer before calling
<code class="function pcre2-api rouge"><span class="nf">pcre2_jit_compile()</span></code>. Alternatively, <code class="function pcre2-api rouge"><span class="nf">pcre2_code_copy()</span></code> or
<code class="function pcre2-api rouge"><span class="nf">pcre2_code_copy_with_tables()</span></code> can be used to obtain a private copy of the
compiled code before calling the JIT compiler.</p></section>
<section class="doc-section level-2"><h3 id="_context_blocks">Context blocks</h3><p>The section <a href="#pcre2-contexts">PCRE2 contexts</a> below introduces the idea of "contexts" in which PCRE2
functions are called. A context is nothing more than a collection of parameters
that control the way PCRE2 operates. Grouping a number of parameters together
in a context is a convenient way of passing them to a PCRE2 function without
using lots of arguments. The parameters that are stored in contexts are in some
sense "advanced features" of the API. Many straightforward applications will
not need to use contexts.</p>
<p>In a multithreaded application, if the parameters in a context are values that
are never changed, the same context can be used by all the threads. However, if
any thread needs to change any value in a context, it must make its own
thread-specific copy.</p></section>
<section class="doc-section level-2"><h3 id="_match_blocks">Match blocks</h3><p>The matching functions need a block of memory for storing the results of a
match. This includes details of what was matched, as well as additional
information such as the name of a <code class="regex rouge"><span class="pcre2-semantic">(*MARK)</span></code> setting. Each thread must provide its
own copy of this memory.</p></section></section>
<section class="doc-section level-1"><h2 id="pcre2-contexts">PCRE2 contexts</h2><p>Some PCRE2 functions have a lot of parameters, many of which are used only by
specialist applications, for example, those that use custom memory management
or non-standard character tables. To keep function argument lists at a
reasonable size, and at the same time to keep the API extensible, "uncommon"
parameters are passed to certain functions in a "context" instead of
directly. A context is just a block of memory that holds the parameter values.
Applications that do not need to adjust any of the context parameters can pass
<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> to operations that accept a context to select their defaults. The
context setter and getter functions require a non-<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> context.
Getter output pointers must also be non-<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>.</p>
<p>The main API uses a general context that is relevant for several PCRE2
operations, a compile-time context, and a match-time context. The experimental
pattern conversion API also has a conversion context, described in
<a href="./pcre2convert.html"><code>pcre2convert</code></a>.</p>
<section class="doc-section level-2"><h3 id="_the_general_context">The general context</h3><p>At present, this context just contains pointers to (and data for) external
memory management functions that are called from several places in the PCRE2
library. The context is named 'general' rather than specifically 'memory'
because in future other fields may be added. If you do not want to supply your
own custom memory management functions, you do not need to bother with a
general context. A general context is created by:</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nf">pcre2_general_context_create</span><span class="p">(</span>
<span class="kt">void</span> <span class="p">*</span><span class="p">(</span><span class="p">*</span><span class="nv">private_malloc</span><span class="p">)(</span><span class="kt">size_t</span> <span class="nv">size</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">memory_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">(</span><span class="p">*</span><span class="nv">private_free</span><span class="p">)(</span><span class="kt">void</span> <span class="p">*</span><span class="nv">ptr</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">memory_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">memory_data</span><span class="p">);</span></code></pre></div>
<p>The two function pointers specify custom memory management functions, whose
prototypes are:</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">void</span> <span class="p">*</span><span class="nf">private_malloc</span><span class="p">(</span><span class="kt">PCRE2_SIZE</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">private_free</span><span class="p">(</span><span class="kt">void</span> <span class="p">*</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="p">);</span></code></pre></div>
<p>Whenever code in PCRE2 calls these functions, the final argument is the value
of <code class="parameter pcre2-api rouge"><span class="nv">memory_data</span></code>. Either of the first two arguments of the creation
function may be <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, in which case the system memory management functions
<code class="c rouge" data-lang="c"><span class="nf">malloc</span><span class="p">()</span></code> and <code class="c rouge" data-lang="c"><span class="nf">free</span><span class="p">()</span></code> are used. (This is not currently useful, as
there are no other fields in a general context, but in future there might be.)
The <code class="c rouge" data-lang="c"><span class="nf">private_malloc</span><span class="p">()</span></code> function is used (if supplied) to obtain memory for
storing the context, and all three values are saved as part of the context.</p>
<p>Whenever PCRE2 creates a data block of any kind, the block contains a pointer
to the <code class="c rouge" data-lang="c"><span class="nf">free</span><span class="p">()</span></code> function that matches the <code class="c rouge" data-lang="c"><span class="nf">malloc</span><span class="p">()</span></code> function that was
used. When the time comes to free the block, this function is called.</p>
<p>A general context can be copied by calling:</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nf">pcre2_general_context_copy</span><span class="p">(</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span></code></pre></div>
<p>The memory used for a general context should be freed by calling:</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">void</span> <span class="nf">pcre2_general_context_free</span><span class="p">(</span><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span></code></pre></div>
<p>If this function is passed a <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> argument, it returns immediately without
doing anything.</p></section>
<section class="doc-section level-2"><h3 id="_the_compile_context">The compile context</h3><p>A compile context is required if you want to provide an external function for
stack checking during compilation or to change the default values of any of the
following compile-time parameters:</p>
<ul class="compact"><li>What <code class="regex rouge"><span class="pcre2-semantic">\R</span></code> matches (Unicode newlines or CR, LF, CRLF only)</li><li>PCRE2’s character tables</li><li>The newline character sequence</li><li>The compile time nested parentheses limit</li><li>The maximum length of the pattern string</li><li>The extra options bits (none set by default)</li><li>Which performance optimizations the compiler should apply</li></ul>
<p>A compile context is also required if you are using custom memory management.
If none of these apply, just pass <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> as the context argument of
<code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>.</p>
<p>A compile context is created, copied, and freed by the following functions:</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nf">pcre2_compile_context_create</span><span class="p">(</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nf">pcre2_compile_context_copy</span><span class="p">(</span>
<span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_compile_context_free</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">);</span></code></pre></div>
<p>A compile context is created with default values for its parameters. These can
be changed by calling the following functions, which return 0 on success, or
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADDATA</span></code> if invalid data is detected. The function
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_optimize()</span></code> returns <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOPTION</span></code> for an invalid
<code class="parameter pcre2-api rouge"><span class="nv">directive</span></code> argument.</p>
<p>The following functions get, respectively, the convention for processing <code class="regex rouge"><span class="pcre2-semantic">\R</span></code>,
the maximum pattern length, the newline convention, and the maximum depth of
nested parentheses. They return 0 and require both arguments to be
non-<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_get_bsr</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span> <span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">value</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_max_pattern_length</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">length</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_newline</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">newline</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_parens_nest_limit</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span></code></pre></div>
<p>The value returned by <code class="function pcre2-api rouge"><span class="nf">pcre2_get_max_pattern_length()</span></code> is the largest
value a <code class="type pcre2-api rouge"><span class="kt">PCRE2_SIZE</span></code> variable can hold when the limit is unlimited. Passing this
value to <code class="function pcre2-api rouge"><span class="nf">pcre2_set_max_pattern_length()</span></code> makes the limit unlimited.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_bsr</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span> <span class="kt">uint32_t</span> <span class="nv">value</span><span class="p">);</span></code></pre></div>
<p>The value must be <code class="constant pcre2-api rouge"><span class="no">PCRE2_BSR_ANYCRLF</span></code>, to specify that <code class="regex rouge"><span class="pcre2-semantic">\R</span></code> matches only CR, LF,
or CRLF, or <code class="constant pcre2-api rouge"><span class="no">PCRE2_BSR_UNICODE</span></code>, to specify that <code class="regex rouge"><span class="pcre2-semantic">\R</span></code> matches any Unicode line
ending sequence. The value is used by the JIT compiler and by the two
interpreted matching functions, <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> and
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_character_tables</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">const</span> <span class="kt">uint8_t</span> <span class="p">*</span><span class="nv">tables</span><span class="p">);</span></code></pre></div>
<p>The value may be <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> to select the default tables; the result of
<code class="function pcre2-api rouge"><span class="nf">pcre2_maketables()</span></code>; or another valid set of PCRE2 character tables.
The <code class="function pcre2-api rouge"><span class="nf">pcre2_maketables()</span></code> function takes a general context and builds tables
in the current locale. Supplied tables must remain valid while the context or
patterns compiled with them are in use.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_compile_extra_options</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">);</span></code></pre></div>
<p>As PCRE2 has developed, almost all the 32 option bits that are available in
the <code class="parameter pcre2-api rouge"><span class="nv">options</span></code> argument of <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> have been used up. To avoid
running out, the compile context contains a set of extra option bits which are
used for some newer, assumed rarer, options. This function sets those bits. It
always sets all the bits (either on or off). It does not modify any existing
setting. The available options are defined in the section
<a href="#extra-compile-options">Extra compile options</a>
below.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_max_pattern_length</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">);</span></code></pre></div>
<p>This sets a maximum length, in code units, for any pattern string that is
compiled with this context. If the pattern is longer, an error is generated.
This facility is provided so that applications that accept patterns from
external sources can limit their size. The default is the largest number that a
<code class="type pcre2-api rouge"><span class="kt">PCRE2_SIZE</span></code> variable can hold, which is effectively unlimited.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_max_pattern_compiled_length</span><span class="p">(</span>
<span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">);</span></code></pre></div>
<p>This sets a maximum size, in bytes, for the memory needed to hold the compiled
version of a pattern that is compiled with this context. If the pattern needs
more memory, an error is generated. This facility is provided so that
applications that accept patterns from external sources can limit the amount of
memory they use. The default is the largest number that a <code class="type pcre2-api rouge"><span class="kt">PCRE2_SIZE</span></code> variable
can hold, which is effectively unlimited.</p>
<p>This limit excludes the fixed, platform-dependent compiled-pattern header.
Therefore, <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_SIZE</span></code> can report a larger total allocation. This limit
does not restrict temporary compilation workspace, JIT code, or separate character
tables.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_max_varlookbehind</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span></code></pre></div>
<p>This sets a maximum length for the number of characters matched by a
variable-length lookbehind assertion. The default is set when PCRE2 is built,
with the ultimate default being 255, the same as Perl. Lookbehind assertions
without a bounding length are not supported.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_newline</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">newline</span><span class="p">);</span></code></pre></div>
<p>This specifies which characters or character sequences are to be recognized as
newlines. The value must be one of <code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_CR</span></code> (carriage return only),
<code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_LF</span></code> (linefeed only), <code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_CRLF</span></code> (the two-character
sequence CR followed by LF), <code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_ANYCRLF</span></code> (any of the above),
<code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_ANY</span></code> (any Unicode newline sequence), or <code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_NUL</span></code> (the
NUL character, that is a binary zero).</p>
<p>A pattern can override the value set in the compile context by starting with a
sequence such as <code class="regex rouge"><span class="pcre2-semantic">(*CRLF)</span></code>. See the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
page for details.</p>
<p>When a pattern is compiled with the <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code> or <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED_MORE</span></code>
option, the newline convention affects the recognition of the end of internal
comments starting with <code class="regex rouge"><span class="pcre2-semantic">#</span></code>. The value is saved with the compiled pattern for
subsequent use by the JIT compiler and by the two interpreted matching
functions, <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> and <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_parens_nest_limit</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span></code></pre></div>
<p>This parameter adjusts the limit, set when PCRE2 is built (default 250), on the
depth of parenthesis nesting in a pattern. This limit stops rogue patterns
using up too much system stack when being compiled. The limit applies to
parentheses of all kinds, not just capturing parentheses.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_compile_recursion_guard</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">int</span> <span class="p">(</span><span class="p">*</span><span class="nv">guard</span><span class="p">)(</span><span class="kt">uint32_t</span> <span class="nv">depth</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">user_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">user_data</span><span class="p">);</span></code></pre></div>
<p>There is at least one application that runs PCRE2 in threads with very limited
system stack, where running out of stack is to be avoided at all costs. The
parenthesis limit above cannot take account of how much stack is actually
available during compilation. For a finer control, you can supply a function
that is called whenever <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> starts to compile a parenthesized
part of a pattern. This function can check the actual stack size (or anything
else that it wants to, of course).</p>
<p>The first argument to the callout function gives the current depth of
nesting, and the second is user data that is set up by the last argument of
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_compile_recursion_guard()</span></code>. The callout function should return
zero if all is well, or non-zero to force an error.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_optimize</span><span class="p">(</span><span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">directive</span><span class="p">);</span></code></pre></div>
<p>PCRE2 can apply various performance optimizations during compilation, in order
to make matching faster. For example, the compiler might convert some regex
constructs into an equivalent construct which <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> can execute
faster. By default, all available optimizations are enabled. However, in rare
cases, one might wish to disable specific optimizations. For example, if it is
known that some optimizations cannot benefit a certain regex, it might be
desirable to disable them, in order to speed up compilation.</p>
<p>The permitted values of <code class="parameter pcre2-api rouge"><span class="nv">directive</span></code> are as follows:</p>
<dl class="values spaced" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_OPTIMIZATION_FULL</span></code></span></dt><dd>Enable all optional performance optimizations. This is the default value.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_OPTIMIZATION_NONE</span></code></span></dt><dd>Disable all optional performance optimizations.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_AUTO_POSSESS</span></code><br><code class="constant pcre2-api rouge"><span class="no">PCRE2_AUTO_POSSESS_OFF</span></code></span></dt><dd>Enable/disable "auto-possessification" of variable quantifiers such as <code class="regex rouge"><span class="pcre2-semantic">*</span></code> and <code class="regex rouge"><span class="pcre2-semantic">+</span></code>.
This optimization, for example, turns <code class="regex rouge"><span class="pcre2-semantic">a+b</span></code> into
<code class="regex rouge"><span class="pcre2-semantic">a++b</span></code> in order to avoid
backtracks into <code class="regex rouge"><span class="pcre2-semantic">a+</span></code> that can never be successful. However, if callouts are in
use, auto-possessification means that some callouts are never taken. You can
disable this optimization if you want the matching functions to do a full,
unoptimized search and run all the callouts.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTSTAR_ANCHOR</span></code><br><code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTSTAR_ANCHOR_OFF</span></code></span></dt><dd><p>Enable/disable an optimization that is applied when <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> is the first significant
item in a top-level branch of a pattern, and all the other branches also start
with <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> or with <code class="regex rouge"><span class="pcre2-semantic">\A</span></code> or <code class="regex rouge"><span class="pcre2-semantic">\G</span></code> or <code class="regex rouge"><span class="pcre2-semantic">^</span></code>. Such a pattern is automatically anchored if
<code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTALL</span></code> is set for all the <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> items and <code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> is not set for any
<code class="regex rouge"><span class="pcre2-semantic">^</span></code> items. Otherwise, the fact that any match must start either at the start of
the subject or following a newline is remembered. Like other optimizations,
this can cause callouts to be skipped.</p><p>Dotstar anchor optimization is automatically disabled for <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> if it is inside an
atomic group or a capture group that is the subject of a backreference, or if
the pattern contains <code class="regex rouge"><span class="pcre2-semantic">(*PRUNE)</span></code> or <code class="regex rouge"><span class="pcre2-semantic">(*SKIP)</span></code>.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_START_OPTIMIZE</span></code><br><code class="constant pcre2-api rouge"><span class="no">PCRE2_START_OPTIMIZE_OFF</span></code></span></dt><dd><p>Enable/disable optimizations which cause matching functions to scan the subject
string for specific code unit values before attempting a match. For example, if
it is known that an unanchored match must start with a specific value, the
matching code searches the subject for that value, and fails immediately if it
cannot find it, without actually running the main matching function. This means
that a special item such as <code class="regex rouge"><span class="pcre2-semantic">(*COMMIT)</span></code> at the start of a pattern is not
considered until after a suitable starting point for the match has been found.
Also, when callouts or <code class="regex rouge"><span class="pcre2-semantic">(*MARK)</span></code> items are in use, these "start-up" optimizations
can cause them to be skipped if the pattern is never actually used. The start-up
optimizations are in effect a pre-scan of the subject that takes place before
the pattern is run.</p><p>Disabling start-up optimizations ensures that in cases where the result is "no
match", the callouts do occur, and that items such as <code class="regex rouge"><span class="pcre2-semantic">(*COMMIT)</span></code> and <code class="regex rouge"><span class="pcre2-semantic">(*MARK)</span></code> are
considered at every possible starting position in the subject string.</p>
<p>Disabling start-up optimizations may change the outcome of a matching operation.
Consider the pattern</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">(*COMMIT)ABC</span></code></pre></div>
<p>When this is compiled, PCRE2 records the fact that a match must start with the
character <code class="subject rouge"><span class="pcre2-semantic">A</span></code>. Suppose the subject string is <code class="subject rouge"><span class="pcre2-semantic">DEFABC</span></code>. The start-up
optimization scans along the subject, finds <code class="subject rouge"><span class="pcre2-semantic">A</span></code> and runs the first match
attempt from there. The <code class="regex rouge"><span class="pcre2-semantic">(*COMMIT)</span></code> item means that the pattern must match the
current starting position, which in this case, it does. However, if the same
match is run without start-up optimizations, the initial scan along the subject
string does not happen. The first match attempt is run starting from <code class="subject rouge"><span class="pcre2-semantic">D</span></code> and
when this fails, <code class="regex rouge"><span class="pcre2-semantic">(*COMMIT)</span></code> prevents any further matches being tried, so the
overall result is "no match".</p>
<p>Another start-up optimization makes use of a minimum length for a matching
subject, which is recorded when possible. Consider the pattern</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">(*MARK:1)B(*MARK:2)(X|Y)</span></code></pre></div>
<p>The minimum length for a match is two characters. If the subject is <code class="subject rouge"><span class="pcre2-semantic">XXBB</span></code>, the
"starting character" optimization skips <code class="subject rouge"><span class="pcre2-semantic">XX</span></code>, then tries to match <code class="subject rouge"><span class="pcre2-semantic">BB</span></code>, which
is long enough. In the process, <code class="regex rouge"><span class="pcre2-semantic">(*MARK:2)</span></code> is encountered and remembered. When
the match attempt fails, the next <code class="subject rouge"><span class="pcre2-semantic">B</span></code> is found, but there is only one character
left, so there are no more attempts, and "no match" is returned with the "last
mark seen" set to <code class="subject rouge"><span class="pcre2-semantic">2</span></code>. Without start-up optimizations, however, matches are
tried at every possible starting position, including at the end of the subject,
where <code class="regex rouge"><span class="pcre2-semantic">(*MARK:1)</span></code> is encountered, but there is no <code class="subject rouge"><span class="pcre2-semantic">B</span></code>, so the "last mark seen"
that is returned is <code class="subject rouge"><span class="pcre2-semantic">1</span></code>. In this case, the optimizations do not affect the
overall match result, which is still "no match", but they do affect the
auxiliary information that is returned.</p></dd></div></dl></section>
<section class="doc-section level-2"><h3 id="match-context">The match context</h3><p>A match context is required if you want to:</p>
<ul class="compact"><li>Set up a callout function</li><li>Set an offset limit for matching an unanchored pattern</li><li>Change the limit on the amount of heap used when matching</li><li>Change the backtracking match limit</li><li>Change the backtracking depth limit</li><li>Set custom memory management specifically for the match</li></ul>
<p>If none of these apply, just pass <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> as the context argument of
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, or <code class="function pcre2-api rouge"><span class="nf">pcre2_jit_match()</span></code>.</p>
<p>A match context is created, copied, and freed by the following functions:</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nf">pcre2_match_context_create</span><span class="p">(</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nf">pcre2_match_context_copy</span><span class="p">(</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_match_context_free</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">);</span></code></pre></div>
<p>A match context is created with default values for its parameters. These can
be changed by calling the following functions, which return 0 on success, or
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADDATA</span></code> if invalid data is detected.</p>
<p>The following functions get, respectively, the backtracking heap limit, match
limit, depth limit, and offset limit. They return 0 and require both arguments
to be non-<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_get_heap_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_match_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_depth_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_get_offset_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">limit</span><span class="p">);</span></code></pre></div>
<p>The value returned by <code class="function pcre2-api rouge"><span class="nf">pcre2_get_offset_limit()</span></code> is the largest value a
<code class="type pcre2-api rouge"><span class="kt">PCRE2_SIZE</span></code> variable can hold when there is no offset limit. Passing this value
to <code class="function pcre2-api rouge"><span class="nf">pcre2_set_offset_limit()</span></code> removes the offset limit.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_callout</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">int</span> <span class="p">(</span><span class="p">*</span><span class="nv">callout</span><span class="p">)(</span>
<span class="kt">pcre2_callout_block</span> <span class="p">*</span><span class="nv">callout_block</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callout_data</span><span class="p">);</span></code></pre></div>
<p>This sets up a callout function for PCRE2 to call at specified points
during a matching operation. Details are given in the
<a href="./pcre2callout.html"><code>pcre2callout</code></a>
documentation.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_substitute_callout</span><span class="p">(</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">int</span> <span class="p">(</span><span class="p">*</span><span class="nv">substitute_callout</span><span class="p">)(</span>
<span class="kt">pcre2_substitute_callout_block</span> <span class="p">*</span><span class="nv">callout_block</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_callout_data</span><span class="p">);</span></code></pre></div>
<p>This sets up a callout function for PCRE2 to call after each substitution
made by <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code>. Details are given in the section
<a href="#creating-substitution-string">Creating a new string with substitutions</a>
below.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_substitute_case_callout</span><span class="p">(</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="nf">PCRE2_SIZE</span> <span class="p">(</span><span class="p">*</span><span class="nv">substitute_case_callout</span><span class="p">)(</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">input</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">input_length</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">output</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">output_capacity</span><span class="p">,</span>
<span class="kt">int</span> <span class="nv">case_operation</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_case_callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_case_callout_data</span><span class="p">);</span></code></pre></div>
<p>This sets up a callout function for PCRE2 to call when performing case
transformations inside <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code>. Details are given in the
section <a href="#creating-substitution-string">Creating a new string with substitutions</a>
below.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_offset_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">limit</span><span class="p">);</span></code></pre></div>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">offset_limit</span></code> parameter limits how far an unanchored search can
advance in the subject string. The default value is <code class="constant pcre2-api rouge"><span class="no">PCRE2_UNSET</span></code>. The
value <code class="constant pcre2-api rouge"><span class="no">PCRE2_UNSET</span></code> removes the limit; any other value must not exceed the
subject length in code units. <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> and <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>
return <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOFFSETLIMITVALUE</span></code> if this requirement is not met.
When the subject length is specified as <code class="constant pcre2-api rouge"><span class="no">PCRE2_ZERO_TERMINATED</span></code>, the limit
is checked against the actual string length. A limit equal to the subject
length is permitted. The setter itself does not check this condition.</p>
<p>For a valid limit, <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> and <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> return
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code> if a match with a starting point before or at the given
offset is not found. The <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> function makes no more
substitutions.</p>
<p>For example, if the pattern <code class="regex rouge"><span class="pcre2-semantic">abc</span></code> is matched against <code class="subject rouge"><span class="pcre2-semantic">123abc</span></code> with an offset
limit less than 3, the result is <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code>. A match can never be
found if the <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> argument of <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>,
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, or <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> is greater than the offset
limit set in the match context.</p>
<p>When using this facility, you must set the <code class="constant pcre2-api rouge"><span class="no">PCRE2_USE_OFFSET_LIMIT</span></code> option when
calling <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> so that when JIT is in use, different code can be
compiled. If a match is started with a non-default match limit when
<code class="constant pcre2-api rouge"><span class="no">PCRE2_USE_OFFSET_LIMIT</span></code> is not set, an error is generated.</p>
<p>The offset limit facility can be used to track progress when searching large
subject strings or to limit the extent of global substitutions. See also the
<code class="constant pcre2-api rouge"><span class="no">PCRE2_FIRSTLINE</span></code> option, which requires a match to start before or at the first
newline that follows the start of matching in the subject. If this is set with
an offset limit, a match must occur in the first line and also within the
offset limit. In other words, whichever limit comes first is used.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_heap_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span></code></pre></div>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">heap_limit</span></code> parameter specifies, in units of kibibytes (1024 bytes),
the maximum amount of heap memory that <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> may use to hold
backtracking information when running an interpretive match. This limit also
applies to <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, which may use the heap when processing
patterns with a lot of nested pattern recursion or lookarounds or atomic
groups. This limit does not apply to matching with the JIT optimization, which
has its own memory control arrangements (see the
<a href="./pcre2jit.html"><code>pcre2jit</code></a>
documentation for more details). If the limit is reached, the negative error
code <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_HEAPLIMIT</span></code> is returned. The default limit can be set when PCRE2
is built; if it is not, the default is set very large and is essentially
unlimited.</p>
<p>A value for the heap limit may also be supplied by an item at the start of a
pattern of the form</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">(*LIMIT_HEAP=<em>ddd</em>)</span></code></pre></div>
<p>where <em>ddd</em> is a decimal number. However, such a setting is ignored unless <em>ddd</em> is
less than the limit set by the caller of <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> or, if no such
limit is set, less than the default.</p>
<p>The <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> function always needs some heap memory, so setting a
value of zero guarantees a "heap limit exceeded" error. Details of how
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> uses the heap are given in the
<a href="./pcre2perform.html"><code>pcre2perform</code></a>
documentation.</p>
<p>For <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, a vector on the system stack is used when
processing pattern recursions, lookarounds, or atomic groups, and only if this
is not big enough is heap memory used. In this case, setting a value of zero
disables the use of the heap.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_match_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span></code></pre></div>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">match_limit</span></code> parameter provides a means of preventing PCRE2 from using
up too many computing resources when processing patterns that are not going to
match, but which have a very large number of possibilities in their search
trees. The classic example is a pattern that uses nested unlimited repeats.</p>
<p>There is an internal counter in <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> that is incremented each
time round its main matching loop. If this value reaches the match limit,
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> returns the negative value <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_MATCHLIMIT</span></code>. This has
the effect of limiting the amount of backtracking that can take place. For
patterns that are not anchored, the count restarts from zero for each position
in the subject string. This limit also applies to <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>,
though the counting is done in a different way.</p>
<p>When <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> is called with a pattern that was successfully
processed by <code class="function pcre2-api rouge"><span class="nf">pcre2_jit_compile()</span></code>, the way in which matching is executed
is entirely different. However, there is still the possibility of runaway
matching that goes on for a very long time, and so the <code class="parameter pcre2-api rouge"><span class="nv">match_limit</span></code> value
is also used in this case (but in a different way) to limit how long the
matching can continue.</p>
<p>The default value for the limit can be set when PCRE2 is built; the default is
10,000,000, which handles all but the most extreme cases. A value for the match
limit may also be supplied by an item at the start of a pattern of the form</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">(*LIMIT_MATCH=<em>ddd</em>)</span></code></pre></div>
<p>where <em>ddd</em> is a decimal number. However, such a setting is ignored unless <em>ddd</em> is
less than the limit set by the caller of <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> or
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> or, if no such limit is set, less than the default.</p>
<div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_depth_limit</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">limit</span><span class="p">);</span></code></pre></div>
<p>This parameter limits the depth of nested backtracking in <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>.
Each time a nested backtracking point is passed, a new memory frame is used
to remember the state of matching at that point. Thus, this parameter
indirectly limits the amount of memory that is used in a match. However,
because the size of each memory frame depends on the number of capturing
parentheses, the actual memory limit varies from pattern to pattern. This limit
was more useful in versions before 10.30, where function recursion was used for
backtracking.</p>
<p>The depth limit is not relevant, and is ignored, when matching is done using
JIT compiled code. However, it is supported by <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, which
uses it to limit the depth of nested internal recursive function calls that
implement atomic groups, lookaround assertions, and pattern recursions. This
limits, indirectly, the amount of system stack that is used. It was more useful
in versions before 10.32, when stack memory was used for local workspace
vectors for recursive function calls. From version 10.32, only local variables
are allocated on the stack and as each call uses only a few hundred bytes, even
a small stack can support quite a lot of recursion.</p>
<p>If the depth of internal recursive function calls is great enough, local
workspace vectors are allocated on the heap from version 10.32 onwards, so the
depth limit also indirectly limits the amount of heap memory that is used. A
recursive pattern such as <code class="regex rouge"><span class="pcre2-semantic">(.(?2))((?1)|)</span></code>, when matched to a very long string
using <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, can use a great deal of memory. However, it is
probably better to limit heap usage directly by calling
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_heap_limit()</span></code>.</p>
<p>The default value for the depth limit can be set when PCRE2 is built; if it is
not, the default is set to the same value as the default for the match limit.
If the limit is exceeded, <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> or <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>
returns <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_DEPTHLIMIT</span></code>. A value for the depth limit may also be
supplied by an item at the start of a pattern of the form</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">(*LIMIT_DEPTH=<em>ddd</em>)</span></code></pre></div>
<p>where <em>ddd</em> is a decimal number. However, such a setting is ignored unless <em>ddd</em> is
less than the limit set by the caller of <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> or
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> or, if no such limit is set, less than the default.</p></section></section>
<section class="doc-section level-1"><h2 id="_checking_build_time_options">Checking build-time options</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_config</span><span class="p">(</span><span class="kt">uint32_t</span> <span class="nv">what</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">where</span><span class="p">);</span></code></pre></div>
<p>The function <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code> makes it possible for a PCRE2 client to find
the value of certain configuration parameters and to discover which optional
features have been compiled into the PCRE2 library. The
<a href="./pcre2build.html"><code>pcre2build</code></a>
documentation has more details about these features.</p>
<p>The first argument for <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code> specifies which information is
required. The second argument is a pointer to memory into which the information
is placed. If <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> is passed, the function returns the amount of memory that is
needed for the requested information. For calls that return numerical values,
the value is in bytes; when requesting these values, <code class="parameter pcre2-api rouge"><span class="nv">where</span></code> should point
to appropriately aligned memory. For calls that return strings, the required
length is given in code units, including the terminating zero.</p>
<p>When requesting information, the returned value from <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code> is
non-negative on success, or the negative error code <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOPTION</span></code> if
the value in the first argument is not recognized. The following information is
available:</p>
<dl class="options spaced" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_BSR</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer whose value indicates what character
sequences the <code class="regex rouge"><span class="pcre2-semantic">\R</span></code> escape sequence matches by default. A value of
<code class="constant pcre2-api rouge"><span class="no">PCRE2_BSR_UNICODE</span></code> means that <code class="regex rouge"><span class="pcre2-semantic">\R</span></code> matches any Unicode line ending sequence; a
value of <code class="constant pcre2-api rouge"><span class="no">PCRE2_BSR_ANYCRLF</span></code> means that <code class="regex rouge"><span class="pcre2-semantic">\R</span></code> matches only CR, LF, or CRLF. The
default can be overridden when a pattern is compiled.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_COMPILED_WIDTHS</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer whose lower bits indicate which code unit
widths were selected when PCRE2 was built. The 1-bit indicates 8-bit support,
and the 2-bit and 4-bit indicate 16-bit and 32-bit support, respectively.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_DEPTHLIMIT</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that gives the default limit for the depth of
nested backtracking in <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> or the depth of nested recursions,
lookarounds, and atomic groups in <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>. Further details are
given with <code class="function pcre2-api rouge"><span class="nf">pcre2_set_depth_limit()</span></code> above.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_EFFECTIVE_LINKSIZE</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that contains the number of bytes the library
uses for internal linkage in compiled regular expressions. Its value is derived
from the value that was provided at build time and that is described below by
<code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_LINKSIZE</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_HEAPLIMIT</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that gives, in kibibytes, the default limit
for the amount of heap memory used by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> or
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>. Further details are given with
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_heap_limit()</span></code> above.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_JIT</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that is set to one if support for just-in-time
compiling is included in the library; otherwise it is set to zero. Note that
having the support in the library does not guarantee that JIT will be used for
any given match, and neither does it guarantee that JIT will actually be able
to function, because it may not be able to allocate executable memory in some
environments. There is a special call to <code class="function pcre2-api rouge"><span class="nf">pcre2_jit_compile()</span></code> that can be
used to check this. See the
<a href="./pcre2jit.html"><code>pcre2jit</code></a>
documentation for more details.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_JITTARGET</span></code></span></dt><dd>The <code class="parameter pcre2-api rouge"><span class="nv">where</span></code> argument should point to a code-unit-aligned buffer. All
previous versions of PCRE2 have required no more than 128 code units of buffer
capacity. However, this requirement is not guaranteed to be maintained, so
applications should call <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code> with <code class="parameter pcre2-api rouge"><span class="nv">where</span></code> set to <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> to
receive the required buffer size, then assert or allocate a suitably-size buffer
for a second call to <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code>. The buffer is filled with a string
that contains the name of the architecture for which the JIT compiler is
configured at build time, for example, a 64-bit ARM CPU that supports the
Armv8.1 extension writes <code>ARM-64 (LSE) 64bit (little endian + unaligned)</code>. If
JIT support is not available, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOPTION</span></code> is returned; otherwise the
number of code units used is returned. This is the length of the string plus one
unit for the terminating zero.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_LINKSIZE</span></code></span></dt><dd><p>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that contains the number of bytes the library
was instructed to use for internal linkage in compiled regular expressions.
When PCRE2 is configured, the value can be set to 2, 3, or 4, with the default
being 2 for most libraries.</p><p>The actual number of bytes used depends on the size of the code units that the
library supports and can be higher. See <code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_EFFECTIVE_LINKSIZE</span></code> above
for details.</p>
<p>The default value of 2 for the 8-bit and 16-bit libraries is sufficient for all
but the most massive patterns, since it allows the size of the compiled pattern
to be up to 65,535 code units. Larger values allow larger regular expressions to
be compiled by those two libraries, but at the expense of slower matching.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_MATCHLIMIT</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that gives the default match limit for
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>. Further details are given with
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_match_limit()</span></code> above.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_NEWLINE</span></code></span></dt><dd><p>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer whose value specifies the default character
sequence that is recognized as meaning "newline". The values are:</p><div class="open-block"><div class="content"><dl class="compact" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_CR</span></code> </span></dt><dd>Carriage return (CR)</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_LF</span></code> </span></dt><dd>Linefeed (LF)</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_CRLF</span></code> </span></dt><dd>Carriage return, linefeed (CRLF)</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_ANY</span></code> </span></dt><dd>Any Unicode line ending</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_ANYCRLF</span></code> </span></dt><dd>Any of CR, LF, or CRLF</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_NUL</span></code> </span></dt><dd>The NUL character (binary zero)</dd></div></dl></div></div>
<p>The default should normally correspond to the standard sequence for your
operating system.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_NEVER_BACKSLASH_C</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that is set to one if the use of <code class="regex rouge"><span class="pcre2-semantic">\C</span></code> was
permanently disabled when PCRE2 was built; otherwise it is set to zero.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_PARENSLIMIT</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that gives the maximum depth of nesting
of parentheses (of any kind) in a pattern. This limit is imposed to cap the
amount of system stack used when a pattern is compiled. It is specified when
PCRE2 is built; the default is 250. This limit does not take into account the
stack that may already be used by the calling application. For finer control
over compilation stack usage, see <code class="function pcre2-api rouge"><span class="nf">pcre2_set_compile_recursion_guard()</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_STACKRECURSE</span></code></span></dt><dd>This parameter is obsolete and should not be used in new code. The output is a
<code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that is always set to zero.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_TABLES_LENGTH</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that gives the length of PCRE2’s character
processing tables in bytes. For details of these tables see the
section <a href="#locale-support">Locale support</a>
below.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_UNICODE_VERSION</span></code></span></dt><dd>The <code class="parameter pcre2-api rouge"><span class="nv">where</span></code> argument should point to a code-unit-aligned buffer. All
previous versions of PCRE2 have required no more than 24 code units of buffer
capacity. However, applications should call <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code> with
<code class="parameter pcre2-api rouge"><span class="nv">where</span></code> set to <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> to receive the required buffer size, then assert or
allocate a suitably-size buffer for a second call to <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code>. If
PCRE2 has been compiled without Unicode support, the buffer is filled with the
text <code>Unicode not supported</code>. Otherwise, the Unicode version string (for
example, <code>8.0.0</code>) is written. The number of code units used is returned. This is
the length of the string plus one unit for the terminating zero.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_UNICODE</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer that is set to one if Unicode support is
available; otherwise it is set to zero. Unicode support implies UTF support.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_VERSION</span></code></span></dt><dd>The <code class="parameter pcre2-api rouge"><span class="nv">where</span></code> argument should point to a code-unit-aligned buffer. All
previous versions of PCRE2 have required no more than 24 code units of buffer
capacity. However, applications should call <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code> with
<code class="parameter pcre2-api rouge"><span class="nv">where</span></code> set to <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> to receive the required buffer size, then assert or
allocate a suitably-size buffer for a second call to <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code>. The
buffer is filled with the PCRE2 version string, zero-terminated. The number of
code units used is returned. This is the length of the string plus one unit for
the terminating zero.</dd></div></dl></section>
<section class="doc-section level-1"><h2 id="compiling-a-pattern">Compiling a pattern</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_code</span> <span class="p">*</span><span class="nf">pcre2_compile</span><span class="p">(</span><span class="kt">PCRE2_SPTR</span> <span class="nv">pattern</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">patlen</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">int</span> <span class="p">*</span><span class="nv">errorptr</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">erroroffset</span><span class="p">,</span>
<span class="kt">pcre2_compile_context</span> <span class="p">*</span><span class="nv">ccontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_code_free</span><span class="p">(</span><span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">);</span>
<span class="kt">pcre2_code</span> <span class="p">*</span><span class="nf">pcre2_code_copy</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">);</span>
<span class="kt">pcre2_code</span> <span class="p">*</span><span class="nf">pcre2_code_copy_with_tables</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">);</span></code></pre></div>
<p>The <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> function compiles a pattern into an internal form.
The pattern is defined by a pointer to a string of code units and a length in
code units. If the pattern is zero-terminated, the length can be specified as
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ZERO_TERMINATED</span></code>. A <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> pattern pointer with a length of zero is treated
as an empty string (<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> with a non-zero length causes an error return). The
function returns a pointer to a block of memory that contains the compiled
pattern and related data, or <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> if an error occurred.</p>
<p>If the compile context argument <code class="parameter pcre2-api rouge"><span class="nv">ccontext</span></code> is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, memory for the compiled
pattern is obtained by calling <code class="c rouge" data-lang="c"><span class="nf">malloc</span><span class="p">()</span></code>. Otherwise, it is obtained from
the same memory function that was used for the compile context. The caller must
free the memory by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_code_free()</span></code> when it is no longer needed.
If <code class="function pcre2-api rouge"><span class="nf">pcre2_code_free()</span></code> is called with a <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> argument, it returns
immediately, without doing anything.</p>
<p>The function <code class="function pcre2-api rouge"><span class="nf">pcre2_code_copy()</span></code> makes a copy of the compiled code in new
memory, using the same memory allocator as was used for the original. However,
if the code has been processed by the JIT compiler (see
below),
the JIT information cannot be copied (because it is position-dependent).
The new copy can initially be used only for non-JIT matching, though it can be
passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_jit_compile()</span></code> if required. If <code class="function pcre2-api rouge"><span class="nf">pcre2_code_copy()</span></code> is
called with a <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> argument, it returns <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>.</p>
<p>The <code class="function pcre2-api rouge"><span class="nf">pcre2_code_copy()</span></code> function provides a way for individual threads in a
multithreaded application to acquire a private copy of shared compiled code.
However, it does not make a copy of the character tables used by the compiled
pattern; the new pattern code points to the same tables as the original code.
(See
"Locale Support"
below for details of these character tables.) In many applications the same
tables are used throughout, so this behaviour is appropriate. Nevertheless,
there are occasions when a copy of a compiled pattern and the relevant tables
are needed. The <code class="function pcre2-api rouge"><span class="nf">pcre2_code_copy_with_tables()</span></code> provides this facility.
Copies of both the code and the tables are made, with the new code pointing to
the new tables. The memory for the new tables is automatically freed when
<code class="function pcre2-api rouge"><span class="nf">pcre2_code_free()</span></code> is called for the new copy of the compiled code. If
<code class="function pcre2-api rouge"><span class="nf">pcre2_code_copy_with_tables()</span></code> is called with a <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> argument, it returns
<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>.</p>
<aside class="admonition-block note" role="note"><h6 class="block-title label-only"><span class="title-label">Note: </span></h6><p>When one of the matching functions is called, pointers to the compiled
pattern and the subject string are set in the match data block so that they can
be referenced by the substring extraction functions after a successful match.
After running a match, you must not free a compiled pattern or a subject string
until after all operations on the
match data block
have taken place, unless, in the case of the subject string, you have used the
<code class="constant pcre2-api rouge"><span class="no">PCRE2_COPY_MATCHED_SUBJECT</span></code> option, which is described in the section
<a href="#match-option-bits">Option bits for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code></a>
below.</p></aside>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">options</span></code> argument for <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> contains various bit
settings that affect the compilation. It should be zero if none of them are
required. The available options are described below. Some of them (in
particular, those that are compatible with Perl, but some others as well) can
also be set and unset from within the pattern (see the detailed description in
the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
documentation).</p>
<p>For those options that can be different in different parts of the pattern, the
contents of the <code class="parameter pcre2-api rouge"><span class="nv">options</span></code> argument specifies their settings at the start of
compilation. The <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code>, and <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code>
options can be set at the time of matching as well as at compile time.</p>
<p>Some additional options and less frequently required compile-time parameters
(for example, the newline setting) can be provided in a compile context (as
described
above).</p>
<p>If <code class="parameter pcre2-api rouge"><span class="nv">errorcode</span></code> or <code class="parameter pcre2-api rouge"><span class="nv">erroroffset</span></code> is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> returns
<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> immediately. Otherwise, the variables to which these point are set to an
error code and an offset (number of code units) within the pattern,
respectively, when <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> returns <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> because a compilation
error has occurred.</p>
<p>There are over 100 positive error codes that <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> may return
if it finds an error in the pattern. There are also some negative error codes
that are used for invalid UTF strings when validity checking is in force. These
are the same as given by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> and <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, and
are described in the
<a href="./pcre2unicode.html"><code>pcre2unicode</code></a>
documentation. There is no separate documentation for the positive error codes,
because the textual error messages that are obtained by calling the
<code class="function pcre2-api rouge"><span class="nf">pcre2_get_error_message()</span></code> function (see "Obtaining a textual error
message"
below)
should be self-explanatory. Macro names starting with <code>PCRE2_ERROR_</code> are defined
for both positive and negative error codes in <code>pcre2.h</code>. When compilation
is successful <code class="c rouge" data-lang="c"><span class="p">*</span><span class="nv">errorptr</span></code> is set to a value that returns the message <code>no
error</code> if passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_get_error_message()</span></code>.</p>
<p>The value returned in <code class="c rouge" data-lang="c"><span class="p">*</span><span class="nv">erroroffset</span></code> is an indication of where in the
pattern an error occurred. When there is no error, zero is returned. A non-zero
value is not necessarily the furthest point in the pattern that was read. For
example, after the error "lookbehind assertion is not fixed length", the error
offset points to the start of the failing assertion. For an invalid UTF-8 or
UTF-16 string, the offset is that of the first code unit of the failing
character.</p>
<p>Some errors are not detected until the whole pattern has been scanned; in these
cases, the offset passed back is the length of the pattern. Note that the
offset is in code units, not characters, even in a UTF mode. It may sometimes
point into the middle of a UTF-8 or UTF-16 character.</p>
<p>This code fragment shows a typical straightforward call to
<code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">re</span><span class="p">;</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">erroffset</span><span class="p">;</span>
<span class="kt">int</span> <span class="nv">errorcode</span><span class="p">;</span>
<span class="nv">re</span> <span class="o">=</span> <span class="nf">pcre2_compile</span><span class="p">(</span>
<span class="s">"^A.*Z"</span><span class="p">,</span> <span class="cm">/* the pattern */</span>
<span class="no">PCRE2_ZERO_TERMINATED</span><span class="p">,</span> <span class="cm">/* the pattern is zero-terminated */</span>
<span class="mi">0</span><span class="p">,</span> <span class="cm">/* default options */</span>
<span class="p">&amp;</span><span class="nv">errorcode</span><span class="p">,</span> <span class="cm">/* for error code */</span>
<span class="p">&amp;</span><span class="nv">erroffset</span><span class="p">,</span> <span class="cm">/* for error offset */</span>
<span class="kc">NULL</span><span class="p">);</span> <span class="cm">/* no compile context */</span></code></pre></div>
<section class="doc-section level-2"><h3 id="_main_compile_options">Main compile options</h3><p>The following names for option bits are defined in the <code>pcre2.h</code> header
file:</p>
<dl class="options spaced" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code></span></dt><dd>If this bit is set, the pattern is forced to be "anchored", that is, it is
constrained to match only at the first matching point in the string that is
being searched (the "subject string"). This effect can also be achieved by
appropriate constructs in the pattern itself, which is the only way to do it in
Perl.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ALLOW_EMPTY_CLASS</span></code></span></dt><dd>By default, for compatibility with Perl, a closing square bracket that
immediately follows an opening one is treated as a data character for the
class. When <code class="constant pcre2-api rouge"><span class="no">PCRE2_ALLOW_EMPTY_CLASS</span></code> is set, it terminates the class, which
therefore contains no characters and so can never match.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_BSUX</span></code></span></dt><dd><p>This option request alternative handling of three escape sequences, which
makes PCRE2’s behaviour more like ECMAScript (JavaScript). When it is set:</p><ol class="arabic compact"><li><code class="regex rouge"><span class="pcre2-semantic">\U</span></code> matches an upper case <code class="subject rouge"><span class="pcre2-semantic">U</span></code> character; by default <code class="regex rouge"><span class="pcre2-semantic">\U</span></code> causes a compile
time error (Perl uses <code class="regex rouge"><span class="pcre2-semantic">\U</span></code> to upper case subsequent characters).</li><li><code class="regex rouge"><span class="pcre2-semantic">\u</span></code> matches a lower case <code class="subject rouge"><span class="pcre2-semantic">u</span></code> character unless it is followed by four
hexadecimal digits, in which case the hexadecimal number defines the code point
to match. By default, <code class="regex rouge"><span class="pcre2-semantic">\u</span></code> causes a compile time error (Perl uses it to upper
case the following character).</li><li><code class="regex rouge"><span class="pcre2-semantic">\x</span></code> matches a lower case <code class="subject rouge"><span class="pcre2-semantic">x</span></code> character unless it is followed by two
hexadecimal digits, in which case the hexadecimal number defines the code point
to match. By default, as in Perl, a hexadecimal number is always expected after
<code class="regex rouge"><span class="pcre2-semantic">\x</span></code>, but it may have one or two digits.</li></ol>
<p>ECMAScript 6 added additional functionality to <code class="regex rouge"><span class="pcre2-semantic">\u</span></code>. This can be accessed using
the <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALT_BSUX</span></code> extra option (see "Extra compile options"
below).
Note that this alternative escape handling applies only to patterns. Neither of
these options affects the processing of replacement strings passed to
<code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code>.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_CIRCUMFLEX</span></code></span></dt><dd>In multiline mode (when <code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> is set), the circumflex metacharacter
matches at the start of the subject (unless <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTBOL</span></code> is set), and also
after any internal newline. However, it does not match after a newline at the
end of the subject, for compatibility with Perl. If you want a multiline
circumflex also to match after a terminating newline, you must set
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_CIRCUMFLEX</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_EXTENDED_CLASS</span></code></span></dt><dd>Alters the parsing of character classes to follow the extended syntax
described by Unicode UTS#18. The <code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_EXTENDED_CLASS</span></code> option has no impact
on the behaviour of the Perl-specific <code class="regex rouge"><span class="pcre2-semantic">(?[...])</span></code> syntax for extended classes,
but instead enables the alternative syntax of extended class behaviour inside
ordinary <code class="regex rouge"><span class="pcre2-semantic">[...]</span></code> character classes. See the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
documentation for details of the character classes supported.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_VERBNAMES</span></code></span></dt><dd>By default, for compatibility with Perl, the name in any verb sequence such as
<code class="regex rouge"><span class="pcre2-semantic">(*MARK:<em>NAME</em>)</span></code> is any sequence of characters that does not include a closing
parenthesis. The name is not processed in any way, and it is not possible to
include a closing parenthesis in the name. However, if the <code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_VERBNAMES</span></code>
option is set, normal backslash processing is applied to verb names and only an
unescaped closing parenthesis terminates the name. A closing parenthesis can be
included in a name either as <code class="regex rouge"><span class="pcre2-semantic">\)</span></code> or between <code class="regex rouge"><span class="pcre2-semantic">\Q</span></code> and <code class="regex rouge"><span class="pcre2-semantic">\E</span></code>. If the <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code>
or <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED_MORE</span></code> option is set with <code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_VERBNAMES</span></code>, unescaped
white space in verb names is skipped and #-comments are recognized, exactly as
in the rest of the pattern.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_AUTO_CALLOUT</span></code></span></dt><dd>If this bit is set, <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> automatically inserts callout items,
all with number 255, before each pattern item, except immediately before or
after an explicit callout in the pattern. For discussion of the callout
facility, see the
<a href="./pcre2callout.html"><code>pcre2callout</code></a>
documentation.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_CASELESS</span></code></span></dt><dd><p>If this bit is set, letters in the pattern match both upper and lower case
letters in the subject. It is equivalent to Perl’s <code class="regex rouge"><span class="pcre2-semantic">/i</span></code> option, and it can be
changed within a pattern by a <code class="regex rouge"><span class="pcre2-semantic">(?i)</span></code> option setting. If either <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> or
<code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> is set, Unicode properties are used for all characters with more than
one other case, and for all characters whose code points are greater than
<span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-6"><code class="character pcre2-api rouge"><span class="sc">U+007F</span></code><span class="character-card" id="pcre2-character-6" role="tooltip" aria-label="DELETE (U+007F)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="DELETE"></span><span class="character-codepoint" data-codepoint="U+007F"></span></span></span>.</p><p>Note that there are two ASCII characters, K and S, that, in addition to
their lower case ASCII equivalents, are case-equivalent with <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-7"><code class="character pcre2-api rouge"><span class="sc">U+212A</span></code><span class="character-card" id="pcre2-character-7" role="tooltip" aria-label="KELVIN SIGN (U+212A)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character="K"></span><span class="character-name" data-character-name="KELVIN SIGN"></span><span class="character-codepoint" data-codepoint="U+212A"></span></span></span> (Kelvin
sign) and <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-8"><code class="character pcre2-api rouge"><span class="sc">U+017F</span></code><span class="character-card" id="pcre2-character-8" role="tooltip" aria-label="LATIN SMALL LETTER LONG S (U+017F)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character="ſ"></span><span class="character-name" data-character-name="LATIN SMALL LETTER LONG S"></span><span class="character-codepoint" data-codepoint="U+017F"></span></span></span> (long S) respectively. If you do not want this case
equivalence, you can suppress it by setting <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_CASELESS_RESTRICT</span></code>.</p>
<p>One language family, Turkish and Azeri, has its own case-insensitivity rules,
which can be selected by setting <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_TURKISH_CASING</span></code>. This alters the
behaviour of the 'i', 'I', <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-9"><code class="character pcre2-api rouge"><span class="sc">U+0130</span></code><span class="character-card" id="pcre2-character-9" role="tooltip" aria-label="LATIN CAPITAL LETTER I WITH DOT ABOVE (U+0130)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character="İ"></span><span class="character-name" data-character-name="LATIN CAPITAL LETTER I WITH DOT ABOVE"></span><span class="character-codepoint" data-codepoint="U+0130"></span></span></span> (capital I with dot above), and <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-10"><code class="character pcre2-api rouge"><span class="sc">U+0131</span></code><span class="character-card" id="pcre2-character-10" role="tooltip" aria-label="LATIN SMALL LETTER DOTLESS I (U+0131)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character="ı"></span><span class="character-name" data-character-name="LATIN SMALL LETTER DOTLESS I"></span><span class="character-codepoint" data-codepoint="U+0131"></span></span></span>
(small dotless i) characters.</p>
<p>For lower valued characters with only one other case, a lookup table is used
for speed. When neither <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> nor <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> is set, a lookup table is used
for all code points less than 256, and higher code points (available only in
16-bit or 32-bit mode) are treated as not having another case.</p>
<p>From release 10.45 <code class="constant pcre2-api rouge"><span class="no">PCRE2_CASELESS</span></code> also affects what some of the letter-related
Unicode property escapes (<code class="regex rouge"><span class="pcre2-semantic">\p</span></code> and <code class="regex rouge"><span class="pcre2-semantic">\P</span></code>) match. The properties <code class="regex rouge"><span class="pcre2-semantic">Lu</span></code> (upper case
letter), <code class="regex rouge"><span class="pcre2-semantic">Ll</span></code> (lower case letter), and <code class="regex rouge"><span class="pcre2-semantic">Lt</span></code> (title case letter) are all treated as
<code class="regex rouge"><span class="pcre2-semantic">Lc</span></code> (cased letter) when <code class="constant pcre2-api rouge"><span class="no">PCRE2_CASELESS</span></code> is set.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_DOLLAR_ENDONLY</span></code></span></dt><dd>If this bit is set, a dollar metacharacter in the pattern matches only at the
end of the subject string. Without this option, a dollar also matches
immediately before a newline at the end of the string (but not before any other
newlines). The <code class="constant pcre2-api rouge"><span class="no">PCRE2_DOLLAR_ENDONLY</span></code> option is ignored if <code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> is
set. There is no equivalent to this option in Perl, and no way to set it within
a pattern.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTALL</span></code></span></dt><dd>If this bit is set, a dot metacharacter in the pattern matches any character,
including one that indicates a newline. However, it only ever matches one
character, even if newlines are coded as CRLF. Without this option, a dot does
not match when the current position in the subject is at a newline. This option
is equivalent to Perl’s <code class="regex rouge"><span class="pcre2-semantic">/s</span></code> option, and it can be changed within a pattern by a
<code class="regex rouge"><span class="pcre2-semantic">(?s)</span></code> option setting. A negative class such as <code class="regex rouge"><span class="pcre2-semantic">[^a]</span></code> always matches newline
characters, and the <code class="regex rouge"><span class="pcre2-semantic">\N</span></code> escape sequence always matches a non-newline character,
independent of the setting of <code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTALL</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_DUPNAMES</span></code></span></dt><dd>If this bit is set, names used to identify capture groups need not be unique.
This can be helpful for certain types of pattern when it is known that only one
instance of the named group can ever be matched. There are more details of
named capture groups below; see also the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
documentation.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code></span></dt><dd><p>If this bit is set, the end of any pattern match must be right at the end of
the string being searched (the "subject string"). If the pattern match
succeeds by reaching <code class="regex rouge"><span class="pcre2-semantic">(*ACCEPT)</span></code>, but does not reach the end of the subject, the
match fails at the current starting point. For unanchored patterns, a new match
is then tried at the next starting point. However, if the match succeeds by
reaching the end of the pattern, but not the end of the subject, backtracking
occurs and an alternative match may be found. Consider these two patterns:</p><div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">.(*ACCEPT)|..
.|..</span></code></pre></div>
<p>If matched against <code class="subject rouge"><span class="pcre2-semantic">abc</span></code> with <code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code> set, the first matches <code class="subject rouge"><span class="pcre2-semantic">c</span></code>
whereas the second matches <code class="subject rouge"><span class="pcre2-semantic">bc</span></code>. The effect of <code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code> can also be
achieved by appropriate constructs in the pattern itself, which is the only way
to do it in Perl.</p>
<p>For DFA matching with <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code> applies only
to the first (that is, the longest) matched string. Other parallel matches,
which are necessarily substrings of the first one, must obviously end before
the end of the subject.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code></span></dt><dd><p>If this bit is set, most white space characters in the pattern are totally
ignored except when escaped, inside a character class, or inside a <code class="regex rouge"><span class="pcre2-semantic">\Q...\E</span></code>
sequence. However, white space is not allowed within sequences such as <code class="regex rouge"><span class="pcre2-semantic">(?&gt;</span></code> that
introduce various parenthesized groups, nor within numerical quantifiers such as
<code class="regex rouge"><span class="pcre2-semantic">{1,3}</span></code>. Ignorable white space is permitted between an item and a following
quantifier and between a quantifier and a following <code class="regex rouge"><span class="pcre2-semantic">+</span></code> that indicates
possessiveness. <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code> is equivalent to Perl’s <code class="regex rouge"><span class="pcre2-semantic">/x</span></code> option, and it can be
changed within a pattern by a <code class="regex rouge"><span class="pcre2-semantic">(?x)</span></code> option setting.</p><p>When PCRE2 is compiled without Unicode support, <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code> recognizes as
white space only those characters with code points less than 256 that are
flagged as white space in its low-character table. The table is normally
created by
<code class="function pcre2-api rouge"><span class="nf">pcre2_maketables()</span></code>,
which uses the <code class="c rouge" data-lang="c"><span class="nf">isspace</span><span class="p">()</span></code> function to identify space characters. In most
ASCII environments, the relevant characters are those with code points <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-11"><code class="character pcre2-api rouge"><span class="sc">0x0009</span></code><span class="character-card" id="pcre2-character-11" role="tooltip" aria-label="CHARACTER TABULATION (U+0009)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="CHARACTER TABULATION"></span><span class="character-codepoint" data-codepoint="U+0009"></span></span></span>
(tab), <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-12"><code class="character pcre2-api rouge"><span class="sc">0x000A</span></code><span class="character-card" id="pcre2-character-12" role="tooltip" aria-label="LINE FEED (U+000A)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="LINE FEED"></span><span class="character-codepoint" data-codepoint="U+000A"></span></span></span> (linefeed), <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-13"><code class="character pcre2-api rouge"><span class="sc">0x000B</span></code><span class="character-card" id="pcre2-character-13" role="tooltip" aria-label="LINE TABULATION (U+000B)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="LINE TABULATION"></span><span class="character-codepoint" data-codepoint="U+000B"></span></span></span> (vertical tab), <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-14"><code class="character pcre2-api rouge"><span class="sc">0x000C</span></code><span class="character-card" id="pcre2-character-14" role="tooltip" aria-label="FORM FEED (U+000C)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="FORM FEED"></span><span class="character-codepoint" data-codepoint="U+000C"></span></span></span> (formfeed), <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-15"><code class="character pcre2-api rouge"><span class="sc">0x000D</span></code><span class="character-card" id="pcre2-character-15" role="tooltip" aria-label="CARRIAGE RETURN (U+000D)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="CARRIAGE RETURN"></span><span class="character-codepoint" data-codepoint="U+000D"></span></span></span>
(carriage return), and <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-16"><code class="character pcre2-api rouge"><span class="sc">0x0020</span></code><span class="character-card" id="pcre2-character-16" role="tooltip" aria-label="SPACE (U+0020)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="SPACE"></span><span class="character-codepoint" data-codepoint="U+0020"></span></span></span> (space).</p>
<p>When PCRE2 is compiled with Unicode support, in addition to these characters,
five more Unicode "Pattern White Space" characters are recognized by
<code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code>. These are <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-17"><code class="character pcre2-api rouge"><span class="sc">U+0085</span></code><span class="character-card" id="pcre2-character-17" role="tooltip" aria-label="NEXT LINE (U+0085)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="NEXT LINE"></span><span class="character-codepoint" data-codepoint="U+0085"></span></span></span> (next line), <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-18"><code class="character pcre2-api rouge"><span class="sc">U+200E</span></code><span class="character-card" id="pcre2-character-18" role="tooltip" aria-label="LEFT-TO-RIGHT MARK (U+200E)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="LEFT-TO-RIGHT MARK"></span><span class="character-codepoint" data-codepoint="U+200E"></span></span></span> (left-to-right mark),
<span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-19"><code class="character pcre2-api rouge"><span class="sc">U+200F</span></code><span class="character-card" id="pcre2-character-19" role="tooltip" aria-label="RIGHT-TO-LEFT MARK (U+200F)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="RIGHT-TO-LEFT MARK"></span><span class="character-codepoint" data-codepoint="U+200F"></span></span></span> (right-to-left mark), <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-20"><code class="character pcre2-api rouge"><span class="sc">U+2028</span></code><span class="character-card" id="pcre2-character-20" role="tooltip" aria-label="LINE SEPARATOR (U+2028)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="LINE SEPARATOR"></span><span class="character-codepoint" data-codepoint="U+2028"></span></span></span> (line separator), and <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-21"><code class="character pcre2-api rouge"><span class="sc">U+2029</span></code><span class="character-card" id="pcre2-character-21" role="tooltip" aria-label="PARAGRAPH SEPARATOR (U+2029)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="PARAGRAPH SEPARATOR"></span><span class="character-codepoint" data-codepoint="U+2029"></span></span></span> (paragraph
separator). This set of characters is the same as recognized by Perl’s <code class="regex rouge"><span class="pcre2-semantic">/x</span></code>
option. Note that the horizontal and vertical space characters that are matched
by the <code class="regex rouge"><span class="pcre2-semantic">\h</span></code> and <code class="regex rouge"><span class="pcre2-semantic">\v</span></code> escapes in patterns are a much bigger set.</p>
<p>As well as ignoring most white space, <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code> also causes characters
between an unescaped # outside a character class and the next newline,
inclusive, to be ignored, which makes it possible to include comments inside
complicated patterns. Note that the end of this type of comment is a literal
newline sequence in the pattern; escape sequences that happen to represent a
newline do not count.</p>
<p>Which characters are interpreted as newlines can be specified by a setting in
the compile context that is passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> or by a special
sequence at the start of the pattern, as described in the section entitled
"Newline conventions"
in the <code>pcre2pattern</code> documentation. A default is defined when PCRE2 is
built.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED_MORE</span></code></span></dt><dd>This option has the effect of <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code>, but, in addition, unescaped space
and horizontal tab characters are ignored inside a character class. Note: only
these two characters are ignored, not the full set of pattern white space
characters that are ignored outside a character class. <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED_MORE</span></code> is
equivalent to Perl’s <code class="regex rouge"><span class="pcre2-semantic">/xx</span></code> option, and it can be changed within a pattern by a
<code class="regex rouge"><span class="pcre2-semantic">(?xx)</span></code> option setting.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_FIRSTLINE</span></code></span></dt><dd>If this option is set, the start of an unanchored pattern match must be before
or at the first newline in the subject string following the start of matching,
though the matched text may continue over the newline. If <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> is
non-zero, the limiting newline is not necessarily the first newline in the
subject. For example, if the subject string is <code class="subject rouge"><span class="pcre2-semantic">abc\nxyz</span></code> (where <code class="regex rouge"><span class="pcre2-semantic">\n</span></code>
represents a single-character newline) a pattern match for <code class="regex rouge"><span class="pcre2-semantic">yz</span></code> succeeds with
<code class="constant pcre2-api rouge"><span class="no">PCRE2_FIRSTLINE</span></code> if <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> is greater than 3. See also
<code class="constant pcre2-api rouge"><span class="no">PCRE2_USE_OFFSET_LIMIT</span></code>, which provides a more general limiting facility. If
<code class="constant pcre2-api rouge"><span class="no">PCRE2_FIRSTLINE</span></code> is set with an offset limit, a match must occur in the first
line and also within the offset limit. In other words, whichever limit comes
first is used. This option has no effect for anchored patterns.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_LITERAL</span></code></span></dt><dd>If this option is set, all meta-characters in the pattern are disabled, and it
is treated as a literal string. Matching literal strings with a regular
expression engine is not the most efficient way of doing it. If you are doing a
lot of literal matching and are worried about efficiency, you should consider
using other approaches. The only other main options that are allowed with
<code class="constant pcre2-api rouge"><span class="no">PCRE2_LITERAL</span></code> are: <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_AUTO_CALLOUT</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_CASELESS</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_FIRSTLINE</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_MATCH_INVALID_UTF</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_START_OPTIMIZE</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code>, and
<code class="constant pcre2-api rouge"><span class="no">PCRE2_USE_OFFSET_LIMIT</span></code>. The extra options <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_MATCH_LINE</span></code> and
<code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_MATCH_WORD</span></code> are also supported. Any other options cause an error.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_MATCH_INVALID_UTF</span></code></span></dt><dd>This option forces <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> (see below) and also enables support for matching
by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> in subject strings that contain invalid UTF sequences.
Note, however, that the 16-bit and 32-bit PCRE2 libraries process strings as
sequences of <code class="type pcre2-api rouge"><span class="kt">uint16_t</span></code> or <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> code points. They cannot find valid UTF
sequences within an arbitrary string of bytes unless such sequences are
suitably aligned. This facility is not supported for DFA matching. For details,
see the
<a href="./pcre2unicode.html"><code>pcre2unicode</code></a>
documentation.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_MATCH_UNSET_BACKREF</span></code></span></dt><dd>If this option is set, a backreference to an unset capture group matches an
empty string (by default this causes the current matching alternative to fail).
A pattern such as <code class="regex rouge"><span class="pcre2-semantic">(\1)(a)</span></code> succeeds when this option is set (assuming it can
find an <code class="subject rouge"><span class="pcre2-semantic">a</span></code> in the subject), whereas it fails by default, for Perl
compatibility. Setting this option makes PCRE2 behave more like ECMAScript (JavaScript).</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code></span></dt><dd><p>By default, for the purposes of matching "start of line" and "end of line",
PCRE2 treats the subject string as consisting of a single line of characters,
even if it actually contains newlines. The "start of line" metacharacter (<code class="regex rouge"><span class="pcre2-semantic">^</span></code>)
matches only at the start of the string, and the "end of line" metacharacter
(<code class="regex rouge"><span class="pcre2-semantic">$</span></code>) matches only at the end of the string, or before a terminating newline
(except when <code class="constant pcre2-api rouge"><span class="no">PCRE2_DOLLAR_ENDONLY</span></code> is set). Note, however, that unless
<code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTALL</span></code> is set, the "any character" metacharacter (<code class="regex rouge"><span class="pcre2-semantic">.</span></code>) does not match at a
newline. This behaviour (for <code class="regex rouge"><span class="pcre2-semantic">^</span></code>, <code class="regex rouge"><span class="pcre2-semantic">$</span></code>, and dot) is the same as Perl.</p><p>When <code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> it is set, the "start of line" and "end of line"
constructs match immediately following or immediately before internal newlines
in the subject string, respectively, as well as at the very start and end. This
is equivalent to Perl’s <code class="regex rouge"><span class="pcre2-semantic">/m</span></code> option, and it can be changed within a pattern by a
<code class="regex rouge"><span class="pcre2-semantic">(?m)</span></code> option setting. Note that the "start of line" metacharacter does not match
after a newline at the end of the subject, for compatibility with Perl.
However, you can change this by setting the <code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_CIRCUMFLEX</span></code> option. If
there are no newlines in a subject string, or no occurrences of <code class="regex rouge"><span class="pcre2-semantic">^</span></code> or <code class="regex rouge"><span class="pcre2-semantic">$</span></code> in a
pattern, setting <code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> has no effect.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEVER_BACKSLASH_C</span></code></span></dt><dd>This option locks out the use of <code class="regex rouge"><span class="pcre2-semantic">\C</span></code> in the pattern that is being compiled.
This escape can cause unpredictable behaviour in UTF-8 or UTF-16 modes, because
it may leave the current matching point in the middle of a multi-code-unit
character. This option may be useful in applications that process patterns from
external sources. Note that there is also a build-time option that permanently
locks out the use of <code class="regex rouge"><span class="pcre2-semantic">\C</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEVER_UCP</span></code></span></dt><dd>This option locks out the use of Unicode properties for handling <code class="regex rouge"><span class="pcre2-semantic">\B</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\b</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\D</span></code>,
<code class="regex rouge"><span class="pcre2-semantic">\d</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\S</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\s</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\W</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\w</span></code>, and some of the POSIX character classes, as described
for the <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> option below. In particular, it prevents the creator of the
pattern from enabling this facility by starting the pattern with <code class="regex rouge"><span class="pcre2-semantic">(*UCP)</span></code>. This
option may be useful in applications that process patterns from external
sources. The option combination <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> and <code class="constant pcre2-api rouge"><span class="no">PCRE2_NEVER_UCP</span></code> causes an error.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEVER_UTF</span></code></span></dt><dd>This option locks out interpretation of the pattern as UTF-8, UTF-16, or
UTF-32, depending on which library is in use. In particular, it prevents the
creator of the pattern from switching to UTF interpretation by starting the
pattern with <code class="regex rouge"><span class="pcre2-semantic">(*UTF)</span></code>. This option may be useful in applications that process
patterns from external sources. The combination of <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> and
<code class="constant pcre2-api rouge"><span class="no">PCRE2_NEVER_UTF</span></code> causes an error.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_AUTO_CAPTURE</span></code></span></dt><dd>If this option is set, it disables the use of numbered capturing parentheses in
the pattern. Any opening parenthesis that is not followed by <code class="regex rouge"><span class="pcre2-semantic">?</span></code> behaves as if it
were followed by <code class="regex rouge"><span class="pcre2-semantic">?:</span></code> but named parentheses can still be used for capturing (and
they acquire numbers in the usual way). This is the same as Perl’s <code class="regex rouge"><span class="pcre2-semantic">/n</span></code> option.
Note that, when this option is set, references to capture groups
(backreferences or recursion/subroutine calls) may only refer to named groups,
though the reference can be by name or by number.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_AUTO_POSSESS</span></code></span></dt><dd><p>If this (deprecated) option is set, it disables "auto-possessification", which
is an optimization that, for example, turns <code class="regex rouge"><span class="pcre2-semantic">a+b</span></code> into
<code class="regex rouge"><span class="pcre2-semantic">a++b</span></code> in order to avoid
backtracks into <code class="regex rouge"><span class="pcre2-semantic">a+</span></code> that can never be successful. However, if callouts are in
use, auto-possessification means that some callouts are never taken. You can
set this option if you want the matching functions to do a full unoptimized
search and run all the callouts, but it is mainly provided for testing
purposes.</p><p>If a compile context is available, it is recommended to use
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_optimize()</span></code> with the <em>directive</em> <code class="constant pcre2-api rouge"><span class="no">PCRE2_AUTO_POSSESS_OFF</span></code> rather
than the compile option <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_AUTO_POSSESS</span></code>. Note that <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_AUTO_POSSESS</span></code>
takes precedence over the <code class="function pcre2-api rouge"><span class="nf">pcre2_set_optimize()</span></code> optimization directives
<code class="constant pcre2-api rouge"><span class="no">PCRE2_AUTO_POSSESS</span></code> and <code class="constant pcre2-api rouge"><span class="no">PCRE2_AUTO_POSSESS_OFF</span></code>.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_DOTSTAR_ANCHOR</span></code></span></dt><dd>If this (deprecated) option is set, it disables an optimization that is applied
when <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> is the first significant item in a top-level branch of a pattern, and
all the other branches also start with <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> or with <code class="regex rouge"><span class="pcre2-semantic">\A</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\G</span></code>, or <code class="regex rouge"><span class="pcre2-semantic">^</span></code>. The
optimization is automatically disabled for <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> if it is inside an atomic group
or a capture group that is the subject of a backreference, or if the pattern
contains <code class="regex rouge"><span class="pcre2-semantic">(*PRUNE)</span></code> or <code class="regex rouge"><span class="pcre2-semantic">(*SKIP)</span></code>. When the optimization is not disabled, such a
pattern is automatically anchored if <code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTALL</span></code> is set for all the <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> items
and <code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> is not set for any <code class="regex rouge"><span class="pcre2-semantic">^</span></code> items. Otherwise, the fact that any
match must start either at the start of the subject or following a newline is
remembered. Like other optimizations, this can cause callouts to be skipped.
(If a compile context is available, it is recommended to use
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_optimize()</span></code> with the <em>directive</em> <code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTSTAR_ANCHOR_OFF</span></code>
instead.)</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_START_OPTIMIZE</span></code></span></dt><dd><p>This is an option whose main effect is at matching time. It does not change
what <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> generates, but it does affect the output of the JIT
compiler. Setting this option is equivalent to calling
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_optimize()</span></code> with the <em>directive</em> parameter set to
<code class="constant pcre2-api rouge"><span class="no">PCRE2_START_OPTIMIZE_OFF</span></code>.</p><p>There are a number of optimizations that may occur at the start of a match, in
order to speed up the process. For example, if it is known that an unanchored
match must start with a specific code unit value, the matching code searches
the subject for that value, and fails immediately if it cannot find it, without
actually running the main matching function. The start-up optimizations are
in effect a pre-scan of the subject that takes place before the pattern is run.</p>
<p>Disabling the start-up optimizations may cause performance to suffer. However,
this may be desirable for patterns which contain callouts or items such as
<code class="regex rouge"><span class="pcre2-semantic">(*COMMIT)</span></code> and <code class="regex rouge"><span class="pcre2-semantic">(*MARK)</span></code>. See the above description of <code class="constant pcre2-api rouge"><span class="no">PCRE2_START_OPTIMIZE_OFF</span></code>
for further details.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code></span></dt><dd><p>When <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> is set, the validity of the pattern as a UTF string is
automatically checked. There are discussions about the validity of
UTF-8 strings,
UTF-16 strings,
and
UTF-32 strings
in the
<a href="./pcre2unicode.html"><code>pcre2unicode</code></a>
document. If an invalid UTF sequence is found, <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> returns a
negative error code.</p><p>If you know that your pattern is a valid UTF string, and you want to skip this
check for performance reasons, you can set the <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code> option. When
it is set, the effect of passing an invalid UTF string as a pattern is
undefined. It may cause your program to crash or loop.</p>
<p>Note that this option can also be passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> and
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, to suppress UTF validity checking of the subject
string.</p>
<p>Note also that setting <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code> at compile time does not disable the
error that is given if an escape sequence for an invalid Unicode code point is
encountered in the pattern. In particular, the so-called "surrogate" code
points (<span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-22"><code class="character pcre2-api rouge"><span class="sc">0xd800</span></code><span class="character-card" id="pcre2-character-22" role="tooltip" aria-label="Surrogate code point (U+D800)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="Surrogate code point"></span><span class="character-codepoint" data-codepoint="U+D800"></span></span></span> to <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-23"><code class="character pcre2-api rouge"><span class="sc">0xdfff</span></code><span class="character-card" id="pcre2-character-23" role="tooltip" aria-label="Surrogate code point (U+DFFF)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="Surrogate code point"></span><span class="character-codepoint" data-codepoint="U+DFFF"></span></span></span>) are invalid. If you want to allow escape sequences
such as <code class="regex rouge"><span class="pcre2-semantic">\x{d800}</span></code> you can set the <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES</span></code> extra
option, as described in the section <a href="#extra-compile-options">Extra compile options</a>
below.
However, this is possible only in UTF-8 and UTF-32 modes, because these values
are not representable in UTF-16.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code></span></dt><dd><p>This option has two effects. Firstly, it change the way PCRE2 processes <code class="regex rouge"><span class="pcre2-semantic">\B</span></code>,
<code class="regex rouge"><span class="pcre2-semantic">\b</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\D</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\d</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\S</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\s</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\W</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\w</span></code>, and some of the POSIX character classes. By
default, only ASCII characters are recognized, but if <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> is set, Unicode
properties are used to classify characters. There are some PCRE2_EXTRA
options (see below) that add finer control to this behaviour. More details are
given in the section
<a href="./pcre2pattern.html#generic-character-types">Generic character types</a>
in the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
page.</p><p>The second effect of <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> is to force the use of Unicode properties for
upper/lower casing operations, even when <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> is not set. This makes it
possible to process strings in the 16-bit UCS-2 code. This option is available
only if PCRE2 has been compiled with Unicode support (which is the default).</p>
<p>The <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_CASELESS_RESTRICT</span></code> option (see above) restricts caseless
matching such that ASCII characters match only ASCII characters and non-ASCII
characters match only non-ASCII characters. The <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_TURKISH_CASING</span></code>
option (see above) alters the matching of the 'i' characters to follow their
behaviour in Turkish and Azeri languages. For further details on
<code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_CASELESS_RESTRICT</span></code> and <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_TURKISH_CASING</span></code>, see the
<a href="./pcre2unicode.html"><code>pcre2unicode</code></a>
page.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_UNGREEDY</span></code></span></dt><dd>This option inverts the "greediness" of the quantifiers so that they are not
greedy by default, but become greedy if followed by <code class="regex rouge"><span class="pcre2-semantic">?</span></code>. It is not compatible
with Perl. It can also be set by a <code class="regex rouge"><span class="pcre2-semantic">(?U)</span></code> option setting within the pattern.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_USE_OFFSET_LIMIT</span></code></span></dt><dd>This option must be set for <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> if
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_offset_limit()</span></code> is going to be used to set a non-default offset
limit in a match context for matches that use this pattern. An error is
generated if an offset limit is set without this option. For more details, see
the description of <code class="function pcre2-api rouge"><span class="nf">pcre2_set_offset_limit()</span></code> in the
section
that describes match contexts. See also the <code class="constant pcre2-api rouge"><span class="no">PCRE2_FIRSTLINE</span></code>
option above.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code></span></dt><dd>This option causes PCRE2 to regard both the pattern and the subject strings
that are subsequently processed as strings of UTF characters instead of
single-code-unit strings. It is available when PCRE2 is built to include
Unicode support (which is the default). If Unicode support is not available,
the use of this option provokes an error. Details of how <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> changes the
behaviour of PCRE2 are given in the
<a href="./pcre2unicode.html"><code>pcre2unicode</code></a>
page. In particular, note that it changes the way <code class="constant pcre2-api rouge"><span class="no">PCRE2_CASELESS</span></code> works.</dd></div></dl></section>
<section class="doc-section level-2"><h3 id="extra-compile-options">Extra compile options</h3><p>The option bits that can be set in a compile context by calling the
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_compile_extra_options()</span></code> function are as follows:</p>
<dl class="options spaced" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK</span></code></span></dt><dd>Since release 10.38 PCRE2 has forbidden the use of <code class="regex rouge"><span class="pcre2-semantic">\K</span></code> within lookaround
assertions, following Perl’s lead. This option is provided to re-enable the
previous behaviour (act in positive lookarounds, ignore in negative ones) in
case anybody is relying on it.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES</span></code></span></dt><dd><p>This option applies when compiling a pattern in UTF-8 or UTF-32 mode. It is
forbidden in UTF-16 mode, and ignored in non-UTF modes. Unicode "surrogate"
code points in the range <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-24"><code class="character pcre2-api rouge"><span class="sc">0xd800</span></code><span class="character-card" id="pcre2-character-24" role="tooltip" aria-label="Surrogate code point (U+D800)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="Surrogate code point"></span><span class="character-codepoint" data-codepoint="U+D800"></span></span></span> to <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-25"><code class="character pcre2-api rouge"><span class="sc">0xdfff</span></code><span class="character-card" id="pcre2-character-25" role="tooltip" aria-label="Surrogate code point (U+DFFF)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="Surrogate code point"></span><span class="character-codepoint" data-codepoint="U+DFFF"></span></span></span> are used in pairs in UTF-16 to encode
code points with values in the range <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-26"><code class="character pcre2-api rouge"><span class="sc">0x10000</span></code><span class="character-card" id="pcre2-character-26" role="tooltip" aria-label="LINEAR B SYLLABLE B008 A (U+10000)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character="𐀀"></span><span class="character-name" data-character-name="LINEAR B SYLLABLE B008 A"></span><span class="character-codepoint" data-codepoint="U+10000"></span></span></span> to <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-27"><code class="character pcre2-api rouge"><span class="sc">0x10ffff</span></code><span class="character-card" id="pcre2-character-27" role="tooltip" aria-label="<noncharacter-10FFFF> (U+10FFFF)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="<noncharacter-10FFFF>"></span><span class="character-codepoint" data-codepoint="U+10FFFF"></span></span></span>. The surrogates cannot
therefore be represented in UTF-16. They can be represented in UTF-8 and
UTF-32, but are defined as invalid code points, and cause errors if encountered
in a UTF-8 or UTF-32 string that is being checked for validity by PCRE2.</p><p>These values also cause errors if encountered in escape sequences such as
<code class="regex rouge"><span class="pcre2-semantic">\x{d912}</span></code> within a pattern. However, it seems that some applications, when
using PCRE2 to check for unwanted characters in UTF-8 strings, explicitly test
for the surrogates using escape sequences. The <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code> option does
not disable the error that occurs, because it applies only to the testing of
input strings for UTF validity.</p>
<p>If the extra option <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES</span></code> is set, surrogate code
point values in UTF-8 and UTF-32 patterns no longer provoke errors and are
incorporated in the compiled pattern. However, they can only match subject
characters if the matching function is called with <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code> set.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALT_BSUX</span></code></span></dt><dd>The original option <code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_BSUX</span></code> causes PCRE2 to process <code class="regex rouge"><span class="pcre2-semantic">\U</span></code>, <code class="regex rouge"><span class="pcre2-semantic">\u</span></code>, and <code class="regex rouge"><span class="pcre2-semantic">\x</span></code> in
the way that ECMAScript (JavaScript) does. Additional functionality was
defined by ECMAScript 6; setting <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALT_BSUX</span></code> has the effect of
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_BSUX</span></code>, but in addition it recognizes <code class="regex rouge"><span class="pcre2-semantic">\u{hhh..}</span></code> as a hexadecimal
character code, where hhh.. is any number of hexadecimal digits.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ASCII_BSD</span></code></span></dt><dd>This option forces <code class="regex rouge"><span class="pcre2-semantic">\d</span></code> to match only ASCII digits, even when <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> is set.
It can be changed within a pattern by means of the <code class="regex rouge"><span class="pcre2-semantic">(?aD)</span></code> option setting.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ASCII_BSS</span></code></span></dt><dd>This option forces <code class="regex rouge"><span class="pcre2-semantic">\s</span></code> to match only ASCII space characters, even when
<code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> is set. It can be changed within a pattern by means of the <code class="regex rouge"><span class="pcre2-semantic">(?aS)</span></code>
option setting.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ASCII_BSW</span></code></span></dt><dd>This option forces <code class="regex rouge"><span class="pcre2-semantic">\w</span></code> to match only ASCII word characters, even when <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code>
is set. It can be changed within a pattern by means of the <code class="regex rouge"><span class="pcre2-semantic">(?aW)</span></code> option
setting.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ASCII_DIGIT</span></code></span></dt><dd>This option forces the POSIX character classes <code class="regex rouge"><span class="pcre2-semantic">[:digit:]</span></code> and <code class="regex rouge"><span class="pcre2-semantic">[:xdigit:]</span></code> to
match only ASCII digits, even when <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> is set. It can be changed within
a pattern by means of the <code class="regex rouge"><span class="pcre2-semantic">(?aT)</span></code> option setting.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ASCII_POSIX</span></code></span></dt><dd>This option forces all the POSIX character classes, including <code class="regex rouge"><span class="pcre2-semantic">[:digit:]</span></code> and
<code class="regex rouge"><span class="pcre2-semantic">[:xdigit:]</span></code>, to match only ASCII characters, even when <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> is set. It can
be changed within a pattern by means of the <code class="regex rouge"><span class="pcre2-semantic">(?aP)</span></code> option setting, but note that
this also sets <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ASCII_DIGIT</span></code> in order to ensure that <code class="regex rouge"><span class="pcre2-semantic">(?-aP)</span></code> unsets
all ASCII restrictions for POSIX classes.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL</span></code></span></dt><dd><p>This is a dangerous option. Use with care. By default, an unrecognized escape
such as <code class="regex rouge"><span class="pcre2-semantic">\j</span></code> or a malformed one such as <code class="regex rouge"><span class="pcre2-semantic">\x{2z}</span></code> causes a compile-time error when
detected by <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>. Perl is somewhat inconsistent in handling
such items: for example, <code class="regex rouge"><span class="pcre2-semantic">\j</span></code> is treated as a literal <code>j</code>, and non-hexadecimal
digits in <code class="regex rouge"><span class="pcre2-semantic">\x{}</span></code> are just ignored, though warnings are given in both cases if
Perl’s warning switch is enabled. However, a malformed octal number after <code class="regex rouge"><span class="pcre2-semantic">\o{</span></code>
always causes an error in Perl.</p><p>If the <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL</span></code> extra option is passed to
<code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>, all unrecognized or malformed escape sequences are
treated as single-character escapes. For example, <code class="regex rouge"><span class="pcre2-semantic">\j</span></code> is a literal <code>j</code> and
<code class="regex rouge"><span class="pcre2-semantic">\x{2z}</span></code> is treated as the literal string <code>x{2z}</code>. Setting this option means
that typos in patterns may go undetected and have unexpected results. Also note
that a sequence such as <code class="regex rouge"><span class="pcre2-semantic">[\N{]</span></code> is interpreted as a malformed attempt at
<code class="regex rouge"><span class="pcre2-semantic">[\N{...}]</span></code> and so is treated as <code class="regex rouge"><span class="pcre2-semantic">[N{]</span></code> whereas <code class="regex rouge"><span class="pcre2-semantic">[\N]</span></code> gives an error because an
unqualified <code class="regex rouge"><span class="pcre2-semantic">\N</span></code> is a valid escape sequence but is not supported in a character
class. To reiterate: this is a dangerous option. Use with great care.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_CASELESS_RESTRICT</span></code></span></dt><dd>When either <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> or <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> is set, caseless matching follows Unicode
rules, which allow for more than two cases per character. There are two
case-equivalent character sets that contain both ASCII and non-ASCII
characters. The ASCII letter S is case-equivalent to <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-28"><code class="character pcre2-api rouge"><span class="sc">U+017f</span></code><span class="character-card" id="pcre2-character-28" role="tooltip" aria-label="LATIN SMALL LETTER LONG S (U+017F)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character="ſ"></span><span class="character-name" data-character-name="LATIN SMALL LETTER LONG S"></span><span class="character-codepoint" data-codepoint="U+017F"></span></span></span> (long S) and the
ASCII letter K is case-equivalent to <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-29"><code class="character pcre2-api rouge"><span class="sc">U+212a</span></code><span class="character-card" id="pcre2-character-29" role="tooltip" aria-label="KELVIN SIGN (U+212A)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character="K"></span><span class="character-name" data-character-name="KELVIN SIGN"></span><span class="character-codepoint" data-codepoint="U+212A"></span></span></span> (Kelvin sign). This option disables
recognition of case-equivalences that cross the ASCII/non-ASCII boundary. In a
caseless match, both characters must either be ASCII or non-ASCII. The option
can be changed within a pattern by the <code class="regex rouge"><span class="pcre2-semantic">(*CASELESS_RESTRICT)</span></code> or <code class="regex rouge"><span class="pcre2-semantic">(?r)</span></code> option
settings.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ESCAPED_CR_IS_LF</span></code></span></dt><dd>There are some legacy applications where the escape sequence <code class="regex rouge"><span class="pcre2-semantic">\r</span></code> in a pattern
is expected to match a newline. If this option is set, <code class="regex rouge"><span class="pcre2-semantic">\r</span></code> in a pattern is
converted to <code class="regex rouge"><span class="pcre2-semantic">\n</span></code> so that it matches a LF (linefeed) instead of a CR (carriage
return) character. The option does not affect a literal CR in the pattern, nor
does it affect CR specified as an explicit code point such as <code class="regex rouge"><span class="pcre2-semantic">\x{0D}</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_MATCH_LINE</span></code></span></dt><dd>This option is provided for use by the <code>-x</code> option of <code>pcre2grep</code>. It
causes the pattern only to match complete lines. This is achieved by
automatically inserting the code for <code class="regex rouge"><span class="pcre2-semantic">^(?:</span></code> at the start of the compiled
pattern and <code class="regex rouge"><span class="pcre2-semantic">)$</span></code> at the end. Thus, when <code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> is set, the matched
line may be in the middle of the subject string. This option can be used with
<code class="constant pcre2-api rouge"><span class="no">PCRE2_LITERAL</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_MATCH_WORD</span></code></span></dt><dd>This option is provided for use by the <code>-w</code> option of <code>pcre2grep</code>. It
causes the pattern only to match strings that have a word boundary at the start
and the end. This is achieved by automatically inserting the code for <code class="regex rouge"><span class="pcre2-semantic">\b(?:</span></code>
at the start of the compiled pattern and <code class="regex rouge"><span class="pcre2-semantic">)\b</span></code> at the end. The option may be
used with <code class="constant pcre2-api rouge"><span class="no">PCRE2_LITERAL</span></code>. However, it is ignored if <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_MATCH_LINE</span></code> is
also set.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_NO_BS0</span></code></span></dt><dd>If this option is set (note that its final character is the digit zero) it locks
out the use of the sequence <code class="regex rouge"><span class="pcre2-semantic">\0</span></code> unless at least one more octal digit follows.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_PYTHON_OCTAL</span></code></span></dt><dd>If this option is set, PCRE2 follows Python’s rules for interpreting octal
escape sequences. The rules for handling sequences such as <code class="regex rouge"><span class="pcre2-semantic">\14</span></code>, which could
be an octal number or a back reference are different. Details are given in the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
documentation.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_NEVER_CALLOUT</span></code></span></dt><dd>If this option is set, PCRE2 treats callouts in the pattern as a syntax error,
returning <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_CALLOUT_CALLER_DISABLED</span></code>. This is useful if the application
knows that a callout will not be provided to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, so that
callouts in the pattern are not silently ignored.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_TURKISH_CASING</span></code></span></dt><dd>This option alters case-equivalence of the 'i' letters to follow the
alphabet used by Turkish and Azeri languages. The option can be changed within
a pattern by the <code class="regex rouge"><span class="pcre2-semantic">(*TURKISH_CASING)</span></code> start-of-pattern setting. Either the UTF or
UCP options must be set. In the 8-bit library, UTF must be set. This option
cannot be combined with <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_CASELESS_RESTRICT</span></code>.</dd></div></dl></section></section>
<section class="doc-section level-1"><h2 id="_just_in_time_jit_compilation">Just-in-time (JIT) compilation</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_jit_compile</span><span class="p">(</span><span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_jit_match</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">PCRE2_SPTR</span> <span class="nv">subject</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">start_offset</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_jit_free_unused_memory</span><span class="p">(</span><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">pcre2_jit_stack</span> <span class="p">*</span><span class="nf">pcre2_jit_stack_create</span><span class="p">(</span>
<span class="kt">size_t</span> <span class="nv">startsize</span><span class="p">,</span> <span class="kt">size_t</span> <span class="nv">maxsize</span><span class="p">,</span>
<span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_jit_stack_assign</span><span class="p">(</span><span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">pcre2_jit_callback</span> <span class="nv">callback</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callback_data</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_jit_stack_free</span><span class="p">(</span><span class="kt">pcre2_jit_stack</span> <span class="p">*</span><span class="nv">jit_stack</span><span class="p">);</span></code></pre></div>
<p>These functions provide support for JIT compilation, which, if the just-in-time
compiler is available, further processes a compiled pattern into machine code
that executes much faster than the <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> interpretive matching
function. Full details are given in the
<a href="./pcre2jit.html"><code>pcre2jit</code></a>
documentation.</p>
<p>JIT compilation is a heavyweight optimization. It can take some time for
patterns to be analyzed, and for one-off matches and simple patterns the
benefit of faster execution might be offset by a much slower compilation time.
Most (but not all) patterns can be optimized by the JIT compiler.</p></section>
<section class="doc-section level-1"><h2 id="locale-support">Locale support</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">const</span> <span class="kt">uint8_t</span> <span class="p">*</span><span class="nf">pcre2_maketables</span><span class="p">(</span><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_maketables_free</span><span class="p">(</span><span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">,</span>
<span class="kt">const</span> <span class="kt">uint8_t</span> <span class="p">*</span><span class="nv">tables</span><span class="p">);</span></code></pre></div>
<p>PCRE2 handles caseless matching, and determines whether characters are letters,
digits, or whatever, by reference to a set of tables, indexed by character code
point. However, this applies only to characters whose code points are less than
256. By default, higher-valued code points never match escapes such as <code class="regex rouge"><span class="pcre2-semantic">\w</span></code> or
<code class="regex rouge"><span class="pcre2-semantic">\d</span></code>.</p>
<p>When PCRE2 is built with Unicode support (the default), certain Unicode
character properties can be tested with <code class="regex rouge"><span class="pcre2-semantic">\p</span></code> and <code class="regex rouge"><span class="pcre2-semantic">\P</span></code>, or, alternatively, the
<code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> option can be set when a pattern is compiled; this causes <code class="regex rouge"><span class="pcre2-semantic">\w</span></code> and
friends to use Unicode property support instead of the built-in tables.
<code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> also causes upper/lower casing operations on characters with code
points greater than 127 to use Unicode properties. These effects apply even
when <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> is not set. There are, however, some PCRE2_EXTRA options (see
above) that can be used to modify or suppress them.</p>
<p>The use of locales with Unicode is discouraged. If you are handling characters
with code points greater than 127, you should either use Unicode support, or
use locales, but not try to mix the two.</p>
<p>PCRE2 contains a built-in set of character tables that are used by default.
These are sufficient for many applications. Normally, the internal tables
recognize only ASCII characters. However, when PCRE2 is built, it is possible
to cause the internal tables to be rebuilt in the default "C" locale of the
local system, which may cause them to be different.</p>
<p>The built-in tables can be overridden by tables supplied by the application
that calls PCRE2. These may be created in a different locale from the default.
As more and more applications change to using Unicode, the need for this locale
support is expected to die away.</p>
<p>External tables are built by calling the <code class="function pcre2-api rouge"><span class="nf">pcre2_maketables()</span></code> function, in
the relevant locale. The only argument to this function is a general context,
which can be used to pass a custom memory allocator. If the argument is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>,
the system <code class="c rouge" data-lang="c"><span class="nf">malloc</span><span class="p">()</span></code> is used. The result can be passed to
<code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> as often as necessary, by creating a compile context and
calling <code class="function pcre2-api rouge"><span class="nf">pcre2_set_character_tables()</span></code> to set the tables pointer therein.</p>
<p>For example, to build and use tables that are appropriate for the French locale
(where accented characters with values greater than 127 are treated as
letters), the following code could be used:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="nf">setlocale</span><span class="p">(</span><span class="no">LC_CTYPE</span><span class="p">,</span> <span class="s">"fr_FR"</span><span class="p">);</span>
<span class="nv">tables</span> <span class="o">=</span> <span class="nf">pcre2_maketables</span><span class="p">(</span><span class="kc">NULL</span><span class="p">);</span>
<span class="nv">ccontext</span> <span class="o">=</span> <span class="nf">pcre2_compile_context_create</span><span class="p">(</span><span class="kc">NULL</span><span class="p">);</span>
<span class="nf">pcre2_set_character_tables</span><span class="p">(</span><span class="nv">ccontext</span><span class="p">,</span> <span class="nv">tables</span><span class="p">);</span>
<span class="nv">re</span> <span class="o">=</span> <span class="nf">pcre2_compile</span><span class="p">(...,</span> <span class="nv">ccontext</span><span class="p">);</span></code></pre></div>
<p>The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
are using Windows, the name for the French locale is "french".</p>
<p>The pointer that is passed (via the compile context) to <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>
is saved with the compiled pattern, and the same tables are used by the
matching functions. Thus, for any single pattern, compilation and matching both
happen in the same locale, but different patterns can be processed in different
locales.</p>
<p>It is the caller’s responsibility to ensure that the memory containing the
tables remains available while they are still in use. When they are no longer
needed, you can discard them using <code class="function pcre2-api rouge"><span class="nf">pcre2_maketables_free()</span></code>, which should
pass as its first parameter the same global context that was used to create the
tables.</p>
<section class="doc-section level-2"><h3 id="_saving_locale_tables">Saving locale tables</h3><p>The tables described above are just a sequence of binary bytes, which makes
them independent of hardware characteristics such as endianness or whether the
processor is 32-bit or 64-bit. A copy of the result of <code class="function pcre2-api rouge"><span class="nf">pcre2_maketables()</span></code>
can therefore be saved in a file or elsewhere and re-used later, even in a
different program or on another computer. The size of the tables (number of
bytes) must be obtained by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_config()</span></code> with the
<code class="constant pcre2-api rouge"><span class="no">PCRE2_CONFIG_TABLES_LENGTH</span></code> option because <code class="function pcre2-api rouge"><span class="nf">pcre2_maketables()</span></code> does not
return this value. Note that the <code>pcre2_dftables</code> program, which is part of
the PCRE2 build system, can be used stand-alone to create a file that contains
a set of binary tables. See the
<code>pcre2build</code>
documentation for details.</p></section></section>
<section class="doc-section level-1"><h2 id="information-about-compiled-pattern">Information about a compiled pattern</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_pattern_info</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">uint32_t</span> <span class="nv">what</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">where</span><span class="p">);</span></code></pre></div>
<p>The <code class="function pcre2-api rouge"><span class="nf">pcre2_pattern_info()</span></code> function returns general information about a
compiled pattern. For information about callouts, see the
section <a href="#information-about-pattern-callouts">Information about a pattern’s callouts</a>.
The first argument for <code class="function pcre2-api rouge"><span class="nf">pcre2_pattern_info()</span></code> is a pointer to the compiled
pattern. The second argument specifies which piece of information is required,
and the third argument is a pointer to a variable to receive the data. If the
third argument is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, the first argument is ignored, and the function returns
the size in bytes of the variable that is required for the information
requested. Otherwise, the yield of the function is zero for success, or one of
the following negative numbers:</p>
<dl class="errors compact" style="--tab-width: 12"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NULL</span></code></span></dt><dd>the argument <code class="parameter pcre2-api rouge"><span class="nv">code</span></code> was <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADMAGIC</span></code></span></dt><dd>the "magic number" was not found</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOPTION</span></code></span></dt><dd>the value of <code class="parameter pcre2-api rouge"><span class="nv">what</span></code> was invalid</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNSET</span></code></span></dt><dd>the requested field is not set</dd></div></dl>
<p>The "magic number" is placed at the start of each compiled pattern as a simple
check against passing an arbitrary memory pointer. Here is a typical call of
<code class="function pcre2-api rouge"><span class="nf">pcre2_pattern_info()</span></code>, to obtain the length of the compiled pattern:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nv">rc</span><span class="p">;</span>
<span class="kt">size_t</span> <span class="nv">length</span><span class="p">;</span>
<span class="nv">rc</span> <span class="o">=</span> <span class="nf">pcre2_pattern_info</span><span class="p">(</span>
<span class="nv">re</span><span class="p">,</span> <span class="cm">/* result of pcre2_compile() */</span>
<span class="no">PCRE2_INFO_SIZE</span><span class="p">,</span> <span class="cm">/* what is required */</span>
<span class="p">&amp;</span><span class="nv">length</span><span class="p">);</span> <span class="cm">/* where to put the data */</span></code></pre></div>
<p>The possible values for the second argument are defined in <code>pcre2.h</code>, and
are as follows:</p>
<dl class="values spaced" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_ALLOPTIONS</span></code><br><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_ARGOPTIONS</span></code><br><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_EXTRAOPTIONS</span></code></span></dt><dd><p>Return copies of the pattern’s options. The third argument should point to a
<code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable. <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_ARGOPTIONS</span></code> returns exactly the options that
were passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>, whereas <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_ALLOPTIONS</span></code> returns
the compile options as modified by any top-level <code class="regex rouge"><span class="pcre2-semantic">(*<em>XXX</em>)</span></code> option settings such as
<code class="regex rouge"><span class="pcre2-semantic">(*UTF)</span></code> at the start of the pattern itself. <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_EXTRAOPTIONS</span></code> returns the
extra options that were set in the compile context by calling the
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_compile_extra_options()</span></code> function.</p>
<p>For example, if the pattern <code class="regex rouge"><span class="pcre2-semantic">(*UTF)abc</span></code> is compiled with the <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code>
option, the result for <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_ALLOPTIONS</span></code> is <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code> and <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code>.
Option settings such as <code class="regex rouge"><span class="pcre2-semantic">(?i)</span></code> that can change within a pattern do not affect the
result of <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_ALLOPTIONS</span></code>, even if they appear right at the start of the
pattern. (This was different in some earlier releases.)</p>
<p>A pattern compiled without <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code> is automatically anchored by PCRE2 if
the first significant item in every top-level branch is one of the following:</p>
<div class="open-block"><div class="content"><dl class="compact" style="--tab-width: 4"><div class="dlist-item"><dt><span><code class="regex rouge"><span class="pcre2-semantic">^</span></code> </span></dt><dd>unless <code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> is set</dd></div><div class="dlist-item"><dt><span><code class="regex rouge"><span class="pcre2-semantic">\A</span></code> </span></dt><dd>always</dd></div><div class="dlist-item"><dt><span><code class="regex rouge"><span class="pcre2-semantic">\G</span></code> </span></dt><dd>always</dd></div><div class="dlist-item"><dt><span><code class="regex rouge"><span class="pcre2-semantic">.*</span></code> </span></dt><dd>sometimes — see below</dd></div></dl></div></div>
<p>When <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> is the first significant item, anchoring is possible only when all the
following are true:</p>
<ol class="loweralpha compact" type="a"><li><code class="regex rouge"><span class="pcre2-semantic">.*</span></code> is not in an atomic group</li><li><code class="regex rouge"><span class="pcre2-semantic">.*</span></code> is not in a capture group that is the subject of a backreference</li><li><code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTALL</span></code> is in force for <code class="regex rouge"><span class="pcre2-semantic">.*</span></code></li><li>Neither <code class="regex rouge"><span class="pcre2-semantic">(*PRUNE)</span></code> nor <code class="regex rouge"><span class="pcre2-semantic">(*SKIP)</span></code> appears in the pattern</li><li><code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_DOTSTAR_ANCHOR</span></code> is not set</li><li>Dotstar anchoring has not been disabled with <code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTSTAR_ANCHOR_OFF</span></code></li></ol>
<p>For patterns that are auto-anchored, the <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code> bit is set in the
options returned for <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_ALLOPTIONS</span></code>.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_BACKREFMAX</span></code></span></dt><dd>Return the number of the highest backreference in the pattern. The third
argument should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable. Named capture groups
acquire numbers as well as names, and these count towards the highest
backreference. Backreferences such as <code class="regex rouge"><span class="pcre2-semantic">\4</span></code> or <code class="regex rouge"><span class="pcre2-semantic">\g{12}</span></code> match the captured
characters of the given group, but in addition, the check that a capture
group is set in a conditional group such as <code class="regex rouge"><span class="pcre2-semantic">(?(3)a|b)</span></code> is also a backreference.
Zero is returned if there are no backreferences.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_BSR</span></code></span></dt><dd>The output is a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer whose value indicates what character sequences
the <code class="regex rouge"><span class="pcre2-semantic">\R</span></code> escape sequence matches. A value of <code class="constant pcre2-api rouge"><span class="no">PCRE2_BSR_UNICODE</span></code> means that <code class="regex rouge"><span class="pcre2-semantic">\R</span></code>
matches any Unicode line ending sequence; a value of <code class="constant pcre2-api rouge"><span class="no">PCRE2_BSR_ANYCRLF</span></code> means
that <code class="regex rouge"><span class="pcre2-semantic">\R</span></code> matches only CR, LF, or CRLF.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_CAPTURECOUNT</span></code></span></dt><dd>Return the highest capture group number in the pattern. In patterns where <code class="regex rouge"><span class="pcre2-semantic">(?|</span></code>
is not used, this is also the total number of capture groups. The third
argument should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_DEPTHLIMIT</span></code></span></dt><dd>If the pattern set a backtracking depth limit by including an item of the form
<code class="regex rouge"><span class="pcre2-semantic">(*LIMIT_DEPTH=<em>nnnn</em>)</span></code> at the start, the value is returned. The third argument
should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer. If no such value has been set, the call to
<code class="function pcre2-api rouge"><span class="nf">pcre2_pattern_info()</span></code> returns the error <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNSET</span></code>. Note that this
limit will only be used during matching if it is less than the limit set or
defaulted by the caller of the match function.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_FIRSTBITMAP</span></code></span></dt><dd>In the absence of a single first code unit for a non-anchored pattern,
<code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> may construct a 256-bit table that defines a fixed set of
values for the first code unit in any match. For example, a pattern that starts
with <code class="regex rouge"><span class="pcre2-semantic">[abc]</span></code> results in a table with three bits set. When code unit values
greater than 255 are supported, the flag bit for 255 means "any code unit of
value 255 or above". If such a table was constructed, a pointer to it is
returned. Otherwise <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> is returned. The third argument should point to a
<code class="c rouge" data-lang="c"><span class="kt">const</span> <span class="kt">uint8_t</span> <span class="p">*</span></code> variable.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_FIRSTCODETYPE</span></code></span></dt><dd>Return information about the first code unit of any matched string, for a
non-anchored pattern. The third argument should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code>
variable. If there is a fixed first value, for example, the letter "c" from a
pattern such as <code class="regex rouge"><span class="pcre2-semantic">(cat|cow|coyote)</span></code>, 1 is returned, and the value can be retrieved
using <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_FIRSTCODEUNIT</span></code>. If there is no fixed first value, but it is
known that a match can occur only at the start of the subject or following a
newline in the subject, 2 is returned. Otherwise, and for anchored patterns, 0
is returned.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_FIRSTCODEUNIT</span></code></span></dt><dd>Return the value of the first code unit of any matched string for a pattern
where <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_FIRSTCODETYPE</span></code> returns 1; otherwise return 0. The third
argument should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable. In the 8-bit library, the
value is always less than 256. In the 16-bit library the value can be up to
<span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-30"><code class="character pcre2-api rouge"><span class="sc">0xffff</span></code><span class="character-card" id="pcre2-character-30" role="tooltip" aria-label="<noncharacter-FFFF> (U+FFFF)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="<noncharacter-FFFF>"></span><span class="character-codepoint" data-codepoint="U+FFFF"></span></span></span>. In the 32-bit library in UTF-32 mode the value can be up to <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-31"><code class="character pcre2-api rouge"><span class="sc">0x10ffff</span></code><span class="character-card" id="pcre2-character-31" role="tooltip" aria-label="<noncharacter-10FFFF> (U+10FFFF)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="<noncharacter-10FFFF>"></span><span class="character-codepoint" data-codepoint="U+10FFFF"></span></span></span>,
and up to <span class="character-info" title="" tabindex="0" aria-describedby="pcre2-character-32"><code class="character pcre2-api rouge"><span class="sc">0xffffffff</span></code><span class="character-card" id="pcre2-character-32" role="tooltip" aria-label="Outside Unicode range (0xffffffff)" aria-hidden="true" data-pagefind-ignore=""><span class="character-glyph" data-character=""></span><span class="character-name" data-character-name="Outside Unicode range"></span><span class="character-codepoint" data-codepoint="0xffffffff"></span></span></span> when not using UTF-32 mode.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_FRAMESIZE</span></code></span></dt><dd>Return the size (in bytes) of the data frames that are used to remember
backtracking positions when the pattern is processed by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>
without the use of JIT. The third argument should point to a <code class="type pcre2-api rouge"><span class="kt">size_t</span></code>
variable. The frame size depends on the number of capturing parentheses in the
pattern. Each additional capture group adds two <code class="type pcre2-api rouge"><span class="kt">PCRE2_SIZE</span></code> variables.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_HASBACKSLASHC</span></code></span></dt><dd>Return 1 if the pattern contains any instances of <code class="regex rouge"><span class="pcre2-semantic">\C</span></code>, otherwise 0. The third
argument should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_HASCRORLF</span></code></span></dt><dd>Return 1 if the pattern contains any explicit matches for CR or LF characters,
otherwise 0. The third argument should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable. An
explicit match is either a literal CR or LF character, or <code class="regex rouge"><span class="pcre2-semantic">\r</span></code> or <code class="regex rouge"><span class="pcre2-semantic">\n</span></code> or one of
the equivalent hexadecimal or octal escape sequences.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_HEAPLIMIT</span></code></span></dt><dd>If the pattern set a heap memory limit by including an item of the form
<code class="regex rouge"><span class="pcre2-semantic">(*LIMIT_HEAP=<em>nnnn</em>)</span></code> at the start, the value is returned. The third argument
should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer. If no such value has been set, the call to
<code class="function pcre2-api rouge"><span class="nf">pcre2_pattern_info()</span></code> returns the error <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNSET</span></code>. Note that this
limit will only be used during matching if it is less than the limit set or
defaulted by the caller of the match function.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_JCHANGED</span></code></span></dt><dd>Return 1 if the <code class="regex rouge"><span class="pcre2-semantic">(?J)</span></code> or <code class="regex rouge"><span class="pcre2-semantic">(?-J)</span></code> option setting is used in the pattern, otherwise 0.
The third argument should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable. <code class="regex rouge"><span class="pcre2-semantic">(?J)</span></code> and
<code class="regex rouge"><span class="pcre2-semantic">(?-J)</span></code> set and unset the local <code class="constant pcre2-api rouge"><span class="no">PCRE2_DUPNAMES</span></code> option, respectively.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_JITSIZE</span></code></span></dt><dd>If the compiled pattern was successfully processed by
<code class="function pcre2-api rouge"><span class="nf">pcre2_jit_compile()</span></code>, return the size of the JIT compiled code, otherwise
return zero. The third argument should point to a <code class="type pcre2-api rouge"><span class="kt">size_t</span></code> variable.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_LASTCODETYPE</span></code></span></dt><dd>Returns 1 if there is a rightmost literal code unit that must exist in any
matched string, other than at its start. The third argument should point to a
<code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable. If there is no such value, 0 is returned. When 1 is
returned, the code unit value itself can be retrieved using
<code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_LASTCODEUNIT</span></code>. For anchored patterns, a last literal value is
recorded only if it follows something of variable length. For example, for the
pattern <code class="regex rouge"><span class="pcre2-semantic">^a\d+z\d+</span></code> the returned value is 1 (with "z" returned from
<code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_LASTCODEUNIT</span></code>), but for <code class="regex rouge"><span class="pcre2-semantic">^a\dz\d</span></code> the returned value is 0.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_LASTCODEUNIT</span></code></span></dt><dd>Return the value of the rightmost literal code unit that must exist in any
matched string, other than at its start, for a pattern where
<code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_LASTCODETYPE</span></code> returns 1. Otherwise, return 0. The third argument
should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_MATCHEMPTY</span></code></span></dt><dd>Return 1 if the pattern might match an empty string, otherwise 0. The third
argument should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable. When a pattern contains
recursive subroutine calls it is not always possible to determine whether or
not it can match an empty string. PCRE2 takes a cautious approach and returns 1
in such cases.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_MATCHLIMIT</span></code></span></dt><dd>If the pattern set a match limit by including an item of the form
<code class="regex rouge"><span class="pcre2-semantic">(*LIMIT_MATCH=<em>nnnn</em>)</span></code> at the start, the value is returned. The third argument
should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> integer. If no such value has been set, the call to
<code class="function pcre2-api rouge"><span class="nf">pcre2_pattern_info()</span></code> returns the error <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNSET</span></code>. Note that this
limit will only be used during matching if it is less than the limit set or
defaulted by the caller of the match function.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_MAXLOOKBEHIND</span></code></span></dt><dd><p>A lookbehind assertion moves back a certain number of characters (not code
units) when it starts to process each of its branches. This request returns the
largest of these backward moves. The third argument should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code>
integer. The simple assertions <code class="regex rouge"><span class="pcre2-semantic">\b</span></code> and <code class="regex rouge"><span class="pcre2-semantic">\B</span></code> require a one-character lookbehind
and cause <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_MAXLOOKBEHIND</span></code> to return 1 in the absence of anything
longer. <code class="regex rouge"><span class="pcre2-semantic">\A</span></code> also registers a one-character lookbehind, though it does not
actually inspect the previous character.</p><p>Note that this information is useful for multi-segment matching only
if the pattern contains no nested lookbehinds. For example, the pattern
<code class="regex rouge"><span class="pcre2-semantic">(?&lt;=a(?&lt;=ba)c)</span></code> returns a maximum lookbehind of 2, but when it is processed, the
first lookbehind moves back by two characters, matches one character, then the
nested lookbehind also moves back by two characters. This puts the matching
point three characters earlier than it was at the start.
<code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_MAXLOOKBEHIND</span></code> is really only useful as a debugging tool. See the
<a href="./pcre2partial.html"><code>pcre2partial</code></a>
documentation for a discussion of multi-segment matching.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_MINLENGTH</span></code></span></dt><dd>If a minimum length for matching subject strings was computed, its value is
returned. Otherwise the returned value is 0. This value is not computed when
<code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_START_OPTIMIZE</span></code> is set. The value is a number of characters, which in
UTF mode may be different from the number of code units. The third argument
should point to a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> variable. The value is a lower bound to the
length of any matching string. There may not be any strings of that length that
do actually match, but every string that does match is at least that long.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_NAMECOUNT</span></code><br><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_NAMEENTRYSIZE</span></code><br><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_NAMETABLE</span></code></span></dt><dd><p>PCRE2 supports the use of named as well as numbered capturing parentheses. The
names are just an additional way of identifying the parentheses, which still
acquire numbers. Several convenience functions such as
<code class="function pcre2-api rouge"><span class="nf">pcre2_substring_get_byname()</span></code> are provided for extracting captured
substrings by name. It is also possible to extract the data directly, by first
converting the name to a number in order to access the correct pointers in the
output vector (described with <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> below). To do the conversion,
you need to use the name-to-number map, which is described by these three
values.</p><p>The map consists of a number of fixed-size entries. <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_NAMECOUNT</span></code> gives the number of entries, and <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_NAMEENTRYSIZE</span></code> gives the size of each entry in code units; both of these return a <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> value. The entry size depends on the length of the longest name.</p>
<p><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_NAMETABLE</span></code> returns a pointer to the first entry of the table. This is a <code class="type pcre2-api rouge"><span class="kt">PCRE2_SPTR</span></code> pointer to a block of code units. In the 8-bit library, the first two bytes of each entry are the number of the capturing parenthesis, most significant byte first. In the 16-bit library, the pointer points to 16-bit code units, the first of which contains the parenthesis number. In the 32-bit library, the pointer points to 32-bit code units, the first of which contains the parenthesis number. The rest of the entry is the corresponding name, zero terminated.</p>
<p>The names are in alphabetical order. If <code class="regex rouge"><span class="pcre2-semantic">(?|</span></code> is used to create multiple capture
groups with the same number, as described in the
section <a href="./pcre2pattern.html#duplicate-group-numbers">Duplicate group numbers</a>
in the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
page, the groups may be given the same name, but there is only one entry in the
table. Different names for groups of the same number are not permitted.</p>
<p>Duplicate names for capture groups with different numbers are permitted, but
only if <code class="constant pcre2-api rouge"><span class="no">PCRE2_DUPNAMES</span></code> is set. They appear in the table in the order in which
they were found in the pattern. In the absence of <code class="regex rouge"><span class="pcre2-semantic">(?|</span></code> this is the order of
increasing number; when <code class="regex rouge"><span class="pcre2-semantic">(?|</span></code> is used this is not necessarily the case because
later capture groups may have lower numbers.</p>
<p>As a simple example of the name/number table, consider the following pattern
after compilation by the 8-bit library (assume <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTENDED</span></code> is set, so white
space — including newlines — is ignored):</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">(?&lt;date&gt; (?&lt;year&gt;(\d\d)?\d\d) -
(?&lt;month&gt;\d\d) - (?&lt;day&gt;\d\d) )</span></code></pre></div>
<p>There are four named capture groups, so the table has four entries, and each
entry in the table is eight bytes long. The table is as follows, with
non-printing bytes shows in hexadecimal, and undefined bytes shown as ??:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="text">00 01 d a t e 00 ??
00 05 d a y 00 ?? ??
00 04 m o n t h 00
00 02 y e a r 00 ??</code></pre></div>
<p>When writing code to extract data from named capture groups using the
name-to-number map, remember that the length of the entries is likely to be
different for each compiled pattern.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_NEWLINE</span></code></span></dt><dd><p>The output is one of the following <code class="type pcre2-api rouge"><span class="kt">uint32_t</span></code> values:</p><dl class="compact" style="--tab-width: 12"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_CR</span></code></span></dt><dd>Carriage return (CR)</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_LF</span></code></span></dt><dd>Linefeed (LF)</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_CRLF</span></code></span></dt><dd>Carriage return, linefeed (CRLF)</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_ANY</span></code></span></dt><dd>Any Unicode line ending</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_ANYCRLF</span></code></span></dt><dd>Any of CR, LF, or CRLF</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_NUL</span></code></span></dt><dd>The NUL character (binary zero)</dd></div></dl>
<p>This identifies the character sequence that will be recognized as meaning
"newline" while matching.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_SIZE</span></code></span></dt><dd>Return the size of the compiled pattern in bytes (for all three libraries). The
third argument should point to a <code class="type pcre2-api rouge"><span class="kt">size_t</span></code> variable. This value includes the
size of the general data block that precedes the code units of the compiled
pattern itself. The value that is used when <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> is getting
memory in which to place the compiled pattern may be slightly larger than the
value returned by this option, because there are cases where the code that
calculates the size has to over-estimate. Processing a pattern with the JIT
compiler does not alter the value returned by this option.</dd></div></dl></section>
<section class="doc-section level-1"><h2 id="information-about-pattern-callouts">Information about a pattern’s callouts</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_callout_enumerate</span><span class="p">(</span>
<span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span>
<span class="kt">int</span> <span class="p">(</span><span class="p">*</span><span class="nv">callback</span><span class="p">)(</span><span class="kt">pcre2_callout_enumerate_block</span> <span class="p">*</span><span class="nv">callout_block</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">callout_data</span><span class="p">);</span></code></pre></div>
<p>A script language that supports the use of string arguments in callouts might
like to scan all the callouts in a pattern before running the match. This can
be done by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_callout_enumerate()</span></code>. The first argument is a
pointer to a compiled pattern, the second points to a callback function, and
the third is arbitrary user data. The callback function is called for every
callout in the pattern in the order in which they appear. Its first argument is
a pointer to a callout enumeration block, and its second argument is the
<code class="parameter pcre2-api rouge"><span class="nv">user_data</span></code> value that was passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_callout_enumerate()</span></code>. The
contents of the callout enumeration block are described in the
<a href="./pcre2callout.html"><code>pcre2callout</code></a>
documentation, which also gives further details about callouts.</p></section>
<section class="doc-section level-1"><h2 id="_serialization_and_precompiling">Serialization and precompiling</h2><p>It is possible to save compiled patterns on disc or elsewhere, and reload them
later, subject to a number of restrictions. The host on which the patterns are
reloaded must be running the same version of PCRE2, with the same code unit
width, and must also have the same endianness, pointer width, and <code class="type pcre2-api rouge"><span class="kt">PCRE2_SIZE</span></code>
type. Before compiled patterns can be saved, they must be converted to a
"serialized" form, which in the case of PCRE2 is really just a bytecode dump.
The functions whose names begin with <code class="c rouge" data-lang="c"><span class="kt">pcre2_serialize_</span></code> are used for
converting to and from the serialized form. They are described in the
<a href="./pcre2serialize.html"><code>pcre2serialize</code></a>
documentation. Note that PCRE2 serialization does not convert compiled patterns
to an abstract format like Java or .NET serialization.</p></section>
<section class="doc-section level-1"><h2 id="_the_match_data_block">The match data block</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nf">pcre2_match_data_create</span><span class="p">(</span>
<span class="kt">uint32_t</span> <span class="nv">oveccount</span><span class="p">,</span> <span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nf">pcre2_match_data_create_from_pattern</span><span class="p">(</span>
<span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">pcre2_general_context</span> <span class="p">*</span><span class="nv">gcontext</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_match_data_free</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span></code></pre></div>
<p>Information about a successful or unsuccessful match is placed in a match
data block, which is an opaque structure that is accessed by function calls. In
particular, the match data block contains a vector of offsets into the subject
string that define the matched parts of the subject. This is known as the
"ovector".</p>
<p>Before calling <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, or
<code class="function pcre2-api rouge"><span class="nf">pcre2_jit_match()</span></code> you must create a match data block by calling one of
the creation functions above. For <code class="function pcre2-api rouge"><span class="nf">pcre2_match_data_create()</span></code>, the first
argument is the number of pairs of offsets in the ovector.</p>
<p>When using <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, one pair of offsets is required to identify the
string that matched the whole pattern, with an additional pair for each
captured substring. For example, a value of 4 creates enough space to record
the matched portion of the subject plus three captured substrings.</p>
<p>When using <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> there may be multiple matched substrings of
different lengths at the same point in the subject. The ovector should be made
large enough to hold as many as are expected.</p>
<p>A minimum of at least 1 pair is imposed by <code class="function pcre2-api rouge"><span class="nf">pcre2_match_data_create()</span></code>, so
it is always possible to return the overall matched string in the case of
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> or the longest match in the case of
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>. The maximum number of pairs is 65,535; if the first
argument of <code class="function pcre2-api rouge"><span class="nf">pcre2_match_data_create()</span></code> is greater than this, 65,535 is
used.</p>
<p>The second argument of <code class="function pcre2-api rouge"><span class="nf">pcre2_match_data_create()</span></code> is a pointer to a
general context, which can specify custom memory management for obtaining the
memory for the match data block. If you are not using custom memory management,
pass <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, which causes <code class="c rouge" data-lang="c"><span class="nf">malloc</span><span class="p">()</span></code> to be used.</p>
<p>For <code class="function pcre2-api rouge"><span class="nf">pcre2_match_data_create_from_pattern()</span></code>, the first argument is a
pointer to a compiled pattern. The ovector is created to be exactly the right
size to hold all the substrings a pattern might capture when matched using
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>. You should not use this call when matching with
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>. The second argument is again a pointer to a general
context, but in this case if <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> is passed, the memory is obtained using the
same allocator that was used for the compiled pattern (custom or default).</p>
<p>A match data block can be used many times, with the same or different compiled
patterns. You can extract information from a match data block after a match
operation has finished, using functions that are described in the sections
<a href="#matched-strings">How <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> returns a string and captured substrings</a>
and
<a href="#other-match-information">Other information about a match</a>
below.</p>
<p>When a call of <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> fails, valid data is available in the match
block only when the error is <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code>, or one
of the error codes for an invalid UTF string. Exactly what is available depends
on the error, and is detailed below.</p>
<p>When one of the matching functions is called, pointers to the compiled pattern
and the subject string are set in the match data block so that they can be
referenced by the extraction functions after a successful match. After running
a match, you must not free a compiled pattern or a subject string until after
all operations on the match data block (for that match) have taken place,
unless, in the case of the subject string, you have used the
<code class="constant pcre2-api rouge"><span class="no">PCRE2_COPY_MATCHED_SUBJECT</span></code> option, which is described in the section
<a href="#match-option-bits">Option bits for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code></a>
below.</p>
<p>When a match data block itself is no longer needed, it should be freed by
calling <code class="function pcre2-api rouge"><span class="nf">pcre2_match_data_free()</span></code>. If this function is called with a <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>
argument, it returns immediately, without doing anything.</p></section>
<section class="doc-section level-1"><h2 id="_memory_use_for_match_data_blocks">Memory use for match data blocks</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">PCRE2_SIZE</span> <span class="nf">pcre2_get_match_data_size</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">PCRE2_SIZE</span> <span class="nf">pcre2_get_match_data_heapframes_size</span><span class="p">(</span>
<span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span></code></pre></div>
<p>The size of a match data block depends on the size of the ovector that it
contains. The function <code class="function pcre2-api rouge"><span class="nf">pcre2_get_match_data_size()</span></code> returns the size, in
bytes, of the block that is its argument.</p>
<p>When <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> runs interpretively (that is, without using JIT), it
makes use of a vector of data frames for remembering backtracking positions.
The size of each individual frame depends on the number of capturing
parentheses in the pattern and can be obtained by calling
<code class="function pcre2-api rouge"><span class="nf">pcre2_pattern_info()</span></code> with the <code class="constant pcre2-api rouge"><span class="no">PCRE2_INFO_FRAMESIZE</span></code> option (see the
section <a href="#information-about-compiled-pattern">Information about a compiled pattern</a>
above).</p>
<p>Heap memory is used for the frames vector; if the initial memory block turns
out to be too small during matching, it is automatically expanded. When
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> returns, the memory is not freed, but remains attached to
the match data block, for use by any subsequent matches that use the same
block. It is automatically freed when the match data block itself is freed.</p>
<p>You can find the current size of the frames vector that a match data block owns
by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_get_match_data_heapframes_size()</span></code>. For a newly created
match data block the size will be zero. Some types of match may require a lot
of frames and thus a large vector; applications that run in environments where
memory is constrained can check this and free the match data block if the heap
frames vector has become too big.</p></section>
<section class="doc-section level-1"><h2 id="_matching_a_pattern_the_traditional_function">Matching a pattern: the traditional function</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_match</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">PCRE2_SPTR</span> <span class="nv">subject</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">start_offset</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">);</span></code></pre></div>
<p>The function <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> is called to match a subject string against a
compiled pattern, which is passed in the <code class="parameter pcre2-api rouge"><span class="nv">code</span></code> argument. You can call
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> with the same <code class="parameter pcre2-api rouge"><span class="nv">code</span></code> argument as many times as you
like, in order to find multiple matches in the subject string or to match
different subject strings with the same pattern.</p>
<p>This function is the main matching facility of the library, and it operates in
a Perl-like manner. For specialist use there is also an alternative matching
function, which is described
below
in the section about the <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> function.</p>
<p>Here is an example of a simple call to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">md</span> <span class="o">=</span> <span class="nf">pcre2_match_data_create</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span> <span class="kc">NULL</span><span class="p">);</span>
<span class="kt">int</span> <span class="nv">rc</span> <span class="o">=</span> <span class="nf">pcre2_match</span><span class="p">(</span>
<span class="nv">re</span><span class="p">,</span> <span class="cm">/* result of pcre2_compile() */</span>
<span class="s">"some string"</span><span class="p">,</span> <span class="cm">/* the subject string */</span>
<span class="mi">11</span><span class="p">,</span> <span class="cm">/* the length of the subject string */</span>
<span class="mi">0</span><span class="p">,</span> <span class="cm">/* start at offset 0 in the subject */</span>
<span class="mi">0</span><span class="p">,</span> <span class="cm">/* default options */</span>
<span class="nv">md</span><span class="p">,</span> <span class="cm">/* the match data block */</span>
<span class="kc">NULL</span><span class="p">);</span> <span class="cm">/* a match context; NULL means use defaults */</span></code></pre></div>
<p>If the subject string is zero-terminated, the length can be given as
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ZERO_TERMINATED</span></code>. A match context must be provided if certain less common
matching parameters are to be changed. For details, see the section
<a href="#match-context">The match context</a>
above.</p>
<section class="doc-section level-2"><h3 id="_the_string_to_be_matched_by_pcre2_match">The string to be matched by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code></h3><p>The subject string is passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> as a pointer in
<code class="parameter pcre2-api rouge"><span class="nv">subject</span></code>, a length in <code class="parameter pcre2-api rouge"><span class="nv">length</span></code>, and a starting offset in
<code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code>. The length and offset are in code units, not characters.
That is, they are in bytes for the 8-bit library, 16-bit code units for the
16-bit library, and 32-bit code units for the 32-bit library, whether or not
UTF processing is enabled. As a special case, if <code class="parameter pcre2-api rouge"><span class="nv">subject</span></code> is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> and
<code class="parameter pcre2-api rouge"><span class="nv">length</span></code> is zero, the subject is assumed to be an empty string. If
<code class="parameter pcre2-api rouge"><span class="nv">length</span></code> is non-zero, an error occurs if <code class="parameter pcre2-api rouge"><span class="nv">subject</span></code> is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>.</p>
<p>If <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> is greater than the length of the subject,
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> returns <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOFFSET</span></code>. When the starting offset is
zero, the search for a match starts at the beginning of the subject, and this
is by far the most common case. In UTF-8 or UTF-16 mode, the starting offset
must point to the start of a character, or to the end of the subject (in UTF-32
mode, one code unit equals one character, so all offsets are valid). Like the
pattern string, the subject may contain binary zeros.</p>
<p>A non-zero starting offset is useful when searching for another match in the
same subject by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> again after a previous success.
Setting <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> differs from passing over a shortened string and
setting <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTBOL</span></code> in the case of a pattern that begins with any kind of
lookbehind. For example, consider the pattern</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">\Biss\B</span></code></pre></div>
<p>which finds occurrences of <code class="subject rouge"><span class="pcre2-semantic">iss</span></code> in the middle of words. (<code class="regex rouge"><span class="pcre2-semantic">\B</span></code> matches only if
the current position in the subject is not a word boundary.) When applied to
the string <code class="subject rouge"><span class="pcre2-semantic">Mississippi</span></code> the first call to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> finds the first
occurrence. If <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> is called again with just the remainder of
the subject, namely <code class="subject rouge"><span class="pcre2-semantic">issippi</span></code>, it does not match, because <code class="regex rouge"><span class="pcre2-semantic">\B</span></code> is always false
at the start of the subject, which is deemed to be a word boundary. However, if
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> is passed the entire string again, but with
<code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> set to 4, it finds the second occurrence of <code class="subject rouge"><span class="pcre2-semantic">iss</span></code> because it
is able to look behind the starting point to discover that it is preceded by a
letter.</p>
<p>Finding all the matches in a subject is tricky when the pattern can match an
empty string. PCRE2 includes a helper API to assist with this; see the
section <a href="#iterating-over-matches">Iterating over all matches</a>
below
for details.</p>
<p>If a non-zero starting offset is passed when the pattern is anchored, a single
attempt to match at the given offset is made. This can only succeed if the
pattern does not require the match to be at the start of the subject. In other
words, the anchoring must be the result of setting the <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code> option or
the use of <code class="regex rouge"><span class="pcre2-semantic">.*</span></code> with <code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTALL</span></code>, not by starting the pattern with <code class="regex rouge"><span class="pcre2-semantic">^</span></code> or <code class="regex rouge"><span class="pcre2-semantic">\A</span></code>.</p></section>
<section class="doc-section level-2"><h3 id="match-option-bits">Option bits for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code></h3><p>The unused bits of the <code class="parameter pcre2-api rouge"><span class="nv">options</span></code> argument for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> must be
zero. The only bits that may be set are <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_COPY_MATCHED_SUBJECT</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_DISABLE_RECURSELOOP_CHECK</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTBOL</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEOL</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEMPTY</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEMPTY_ATSTART</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_JIT</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_HARD</span></code>, and <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_SOFT</span></code>.
Their action is described below.</p>
<p>Setting <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code> or <code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code> at match time is not supported by
the just-in-time (JIT) compiler. If it is set, JIT matching is disabled and the
interpretive code in <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> is run.
<code class="constant pcre2-api rouge"><span class="no">PCRE2_DISABLE_RECURSELOOP_CHECK</span></code> is ignored by JIT, but apart from <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_JIT</span></code>
(obviously), the remaining options are supported for JIT matching.</p>
<dl class="options spaced" style="--tab-width: 12"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code></span></dt><dd>The <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code> option limits <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> to matching at the first
matching position. If a pattern was compiled with <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code>, or turned out
to be anchored by virtue of its contents, it cannot be made unanchored at
matching time. Note that setting the option at match time disables JIT
matching.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_COPY_MATCHED_SUBJECT</span></code></span></dt><dd>By default, a pointer to the subject is remembered in the match data block so
that, after a successful match, it can be referenced by the substring
extraction functions. This means that the subject’s memory must not be freed
until all such operations are complete. For some applications where the
lifetime of the subject string is not guaranteed, it may be necessary to make a
copy of the subject string, but it is wasteful to do this unless the match is
successful. After a successful match, if <code class="constant pcre2-api rouge"><span class="no">PCRE2_COPY_MATCHED_SUBJECT</span></code> is set, the
subject is copied and the new pointer is remembered in the match data block
instead of the original subject pointer. The memory allocator that was used for
the match block itself is used. The copy is automatically freed when
<code class="function pcre2-api rouge"><span class="nf">pcre2_match_data_free()</span></code> is called to free the match data block. It is also
automatically freed if the match data block is re-used for another match
operation.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_DISABLE_RECURSELOOP_CHECK</span></code></span></dt><dd><p>This option is relevant only to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> for interpretive matching.
It is ignored when JIT is used, and is forbidden for <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>.</p><p>The use of recursion in patterns can lead to infinite loops. In the
interpretive matcher these would be eventually caught by the match or heap
limits, but this could take a long time and/or use a lot of memory if the
limits are large. There is therefore a check at the start of each recursion.
If the same group is still active from a previous call, and the current subject
pointer is the same as it was at the start of that group, and the furthest
inspected character of the subject has not changed, an error is generated.</p>
<p>There are rare cases of matches that would complete, but nevertheless trigger
this error. This option disables the check. It is provided mainly for testing
when comparing JIT and interpretive behaviour.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code></span></dt><dd>If the <code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code> option is set, any string that <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>
matches must be right at the end of the subject string. Note that setting the
option at match time disables JIT matching.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTBOL</span></code></span></dt><dd>This option specifies that first character of the subject string is not the
beginning of a line, so the circumflex metacharacter should not match before
it. Setting this without having set <code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> at compile time causes
circumflex never to match. This option affects only the behaviour of the
circumflex metacharacter. It does not affect <code class="regex rouge"><span class="pcre2-semantic">\A</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEOL</span></code></span></dt><dd>This option specifies that the end of the subject string is not the end of a
line, so the dollar metacharacter should not match it nor (except in multiline
mode) a newline immediately before it. Setting this without having set
<code class="constant pcre2-api rouge"><span class="no">PCRE2_MULTILINE</span></code> at compile time causes dollar never to match. This option
affects only the behaviour of the dollar metacharacter. It does not affect <code class="regex rouge"><span class="pcre2-semantic">\Z</span></code>
or <code class="regex rouge"><span class="pcre2-semantic">\z</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEMPTY</span></code></span></dt><dd><p>An empty string is not considered to be a valid match if this option is set. If
there are alternatives in the pattern, they are tried. If all the alternatives
match the empty string, the entire match fails. For example, if the pattern</p><p><code class="regex rouge"><span class="pcre2-semantic">a?b?</span></code></p>
<p>is applied to a string not beginning with <code class="subject rouge"><span class="pcre2-semantic">a</span></code> or <code class="subject rouge"><span class="pcre2-semantic">b</span></code>, it matches an empty
string at the start of the subject. With <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEMPTY</span></code> set, this match is not
valid, so <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> searches further into the string for occurrences
of <code class="subject rouge"><span class="pcre2-semantic">a</span></code> or <code class="subject rouge"><span class="pcre2-semantic">b</span></code>.</p></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEMPTY_ATSTART</span></code></span></dt><dd>This is like <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEMPTY</span></code>, except that it locks out an empty string match
only at the first matching position, that is, at the start of the subject plus
the starting offset. An empty string match later in the subject is permitted.
If the pattern is anchored, such a match can occur only if the pattern contains
<code class="regex rouge"><span class="pcre2-semantic">\K</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_JIT</span></code></span></dt><dd>By default, if a pattern has been successfully processed by
<code class="function pcre2-api rouge"><span class="nf">pcre2_jit_compile()</span></code>, JIT is automatically used when <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>
is called with options that JIT supports. Setting <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_JIT</span></code> disables the use
of JIT; it forces matching to be done by the interpreter.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code></span></dt><dd><p>When <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> is set at compile time, the validity of the subject as a UTF
string is checked unless <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code> is passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> or
<code class="constant pcre2-api rouge"><span class="no">PCRE2_MATCH_INVALID_UTF</span></code> was passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code>. The latter special
case is discussed in detail in the
<a href="./pcre2unicode.html"><code>pcre2unicode</code></a>
documentation.</p><p>In the default case, if a non-zero starting offset is given, the check is
applied only to that part of the subject that could be inspected during
matching, and there is a check that the starting offset points to the first
code unit of a character or to the end of the subject. If there are no
lookbehind assertions in the pattern, the check starts at the starting offset.
Otherwise, it starts at the length of the longest lookbehind before the
starting offset, or at the start of the subject if there are not that many
characters before the starting offset. Note that the sequences <code class="regex rouge"><span class="pcre2-semantic">\b</span></code> and <code class="regex rouge"><span class="pcre2-semantic">\B</span></code> are
one-character lookbehinds.</p>
<p>The check is carried out before any other processing takes place, and a
negative error code is returned if the check fails. There are several UTF error
codes for each code unit width, corresponding to different problems with the
code unit sequence. There are discussions about the validity of
UTF-8 strings,
UTF-16 strings,
and
UTF-32 strings
in the
<a href="./pcre2unicode.html"><code>pcre2unicode</code></a>
documentation.</p>
<p>If you know that your subject is valid, and you want to skip this check for
performance reasons, you can set the <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code> option when calling
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>. You might want to do this for the second and subsequent
calls to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> if you are making repeated calls to find multiple
matches in the same subject string.</p>
<section class="admonition-block warning" role="doc-notice"><h6 class="block-title label-only"><span class="title-label">Warning: </span></h6><p>Unless <code class="constant pcre2-api rouge"><span class="no">PCRE2_MATCH_INVALID_UTF</span></code> was set at compile time, when
<code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code> is set at match time the effect of passing an invalid
string as a subject, or an invalid value of <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code>, is undefined.
Your program may crash or loop indefinitely or give wrong results.</p></section></dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_HARD</span></code><br><code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_SOFT</span></code></span></dt><dd><p>These options turn on the partial matching feature. A partial match occurs if
the end of the subject string is reached successfully, but there are not enough
subject characters to complete the match. In addition, either at least one
character must have been inspected or the pattern must contain a lookbehind, or
the pattern must be one that could match an empty string.</p><p>If this situation arises when <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_SOFT</span></code> (but not <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_HARD</span></code>)
is set, matching continues by testing any remaining alternatives. Only if no
complete match can be found is <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code> returned instead of
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code>. In other words, <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_SOFT</span></code> specifies that the
caller is prepared to handle a partial match, but only if no complete match can
be found.</p>
<p>If <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_HARD</span></code> is set, it overrides <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_SOFT</span></code>. In this case, if
a partial match is found, <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> immediately returns
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code>, without considering any other alternatives. In other
words, when <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_HARD</span></code> is set, a partial match is considered to be more
important than an alternative complete match.</p>
<p>There is a more detailed discussion of partial and multi-segment matching, with
examples, in the
<a href="./pcre2partial.html"><code>pcre2partial</code></a>
documentation.</p></dd></div></dl></section></section>
<section class="doc-section level-1"><h2 id="_newline_handling_when_matching">Newline handling when matching</h2><p>When PCRE2 is built, a default newline convention is set; this is usually the
standard convention for the operating system. The default can be overridden in
a
compile context
by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_set_newline()</span></code>. It can also be overridden by starting a
pattern string with, for example, <code class="regex rouge"><span class="pcre2-semantic">(*CRLF)</span></code>, as described in the
section <a href="./pcre2pattern.html#newline-conventions">Newline conventions</a>
in the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
page. During matching, the newline choice affects the behaviour of the dot,
circumflex, and dollar metacharacters. It may also alter the way the match
starting position is advanced after a match failure for an unanchored pattern.</p>
<p>When <code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_CRLF</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_ANYCRLF</span></code>, or <code class="constant pcre2-api rouge"><span class="no">PCRE2_NEWLINE_ANY</span></code> is set as
the newline convention, and a match attempt for an unanchored pattern fails
when the current starting position is at a CRLF sequence, and the pattern
contains no explicit matches for CR or LF characters, the match position is
advanced by two characters instead of one, in other words, to after the CRLF.</p>
<p>The above rule is a compromise that makes the most common cases work as
expected. For example, if the pattern is <code class="regex rouge"><span class="pcre2-semantic">.+A</span></code> (and the <code class="constant pcre2-api rouge"><span class="no">PCRE2_DOTALL</span></code> option is
not set), it does not match the string <code class="subject rouge"><span class="pcre2-semantic">\r\nA</span></code> because, after failing at the
start, it skips both the CR and the LF before retrying. However, the pattern
<code class="regex rouge"><span class="pcre2-semantic">[\r\n]A</span></code> does match that string, because it contains an explicit CR or LF
reference, and so advances only by one character after the first failure.</p>
<p>An explicit match for CR of LF is either a literal appearance of one of those
characters in the pattern, or one of the <code class="regex rouge"><span class="pcre2-semantic">\r</span></code> or <code class="regex rouge"><span class="pcre2-semantic">\n</span></code> or equivalent octal or
hexadecimal escape sequences. Implicit matches such as <code class="regex rouge"><span class="pcre2-semantic">[^X]</span></code> do not count, nor
does <code class="regex rouge"><span class="pcre2-semantic">\s</span></code>, even though it includes CR and LF in the characters that it matches.</p>
<p>Notwithstanding the above, anomalous effects may still occur when CRLF is a
valid newline sequence and explicit <code class="regex rouge"><span class="pcre2-semantic">\r</span></code> or <code class="regex rouge"><span class="pcre2-semantic">\n</span></code> escapes appear in the pattern.</p></section>
<section class="doc-section level-1"><h2 id="matched-strings">How <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> returns a string and captured substrings</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">uint32_t</span> <span class="nf">pcre2_get_ovector_count</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nf">pcre2_get_ovector_pointer</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span></code></pre></div>
<p>In general, a pattern matches a certain portion of the subject, and in
addition, further substrings from the subject may be picked out by
parenthesized parts of the pattern. Following the usage in Jeffrey Friedl’s
book, this is called "capturing" in what follows, and the phrase "capture
group" (Perl terminology) is used for a fragment of a pattern that picks out a
substring. PCRE2 supports several other kinds of parenthesized group that do
not cause substrings to be captured. The <code class="function pcre2-api rouge"><span class="nf">pcre2_pattern_info()</span></code> function
can be used to find out how many capture groups there are in a compiled
pattern.</p>
<p>You can use auxiliary functions for accessing captured substrings
by number
or
by name,
as described in sections below.</p>
<p>Alternatively, you can make direct use of the vector of <code class="type pcre2-api rouge"><span class="kt">PCRE2_SIZE</span></code> values,
called the ovector, which contains the offsets of captured strings. It is
part of the
match data block.
The function <code class="function pcre2-api rouge"><span class="nf">pcre2_get_ovector_pointer()</span></code> returns the address of the
ovector, and <code class="function pcre2-api rouge"><span class="nf">pcre2_get_ovector_count()</span></code> returns the number of pairs of
values it contains.</p>
<p>Within the ovector, the first in each pair of values is set to the offset of
the first code unit of a substring, and the second is set to the offset of the
first code unit after the end of a substring. These values are always code unit
offsets, not character offsets. That is, they are byte offsets in the 8-bit
library, 16-bit offsets in the 16-bit library, and 32-bit offsets in the 32-bit
library.</p>
<p>After a partial match (error return <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code>), only the first pair
of offsets (that is, <code class="c rouge" data-lang="c"><span class="nv">ovector</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span></code> and <code class="c rouge" data-lang="c"><span class="nv">ovector</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span></code>) are set. They
identify the part of the subject that was partially matched. See the
<a href="./pcre2partial.html"><code>pcre2partial</code></a>
documentation for details of partial matching.</p>
<p>After a fully successful match, the first pair of offsets identifies the
portion of the subject string that was matched by the entire pattern. The next
pair is used for the first captured substring, and so on. The value returned by
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> is one more than the highest numbered pair that has been
set. For example, if two substrings have been captured, the returned value is
3. If there are no captured substrings, the return value from a successful
match is 1, indicating that just the first pair of offsets has been set.</p>
<p>If a pattern uses the <code class="regex rouge"><span class="pcre2-semantic">\K</span></code> escape sequence within a positive lookahead assertion,
the reported start of a successful match can be greater than the end of the
match. For example, if the pattern <code class="regex rouge"><span class="pcre2-semantic">(?=ab\K)</span></code> is matched against <code class="subject rouge"><span class="pcre2-semantic">ab</span></code>, the start
and end offset values for the match are 2 and 0.</p>
<p>If a capture group is matched repeatedly within a single match operation, it is
the last portion of the subject that it matched that is returned.</p>
<p>If the ovector is too small to hold all the captured substring offsets, as much
as possible is filled in, and the function returns a value of zero. If captured
substrings are not of interest, <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> may be called with a match
data block whose ovector is of minimum length (that is, one pair).</p>
<p>It is possible for capture group number <em>n+1</em> to match some part of the
subject when group <em>n</em> has not been used at all. For example, if the string
<code class="subject rouge"><span class="pcre2-semantic">abc</span></code> is matched against the pattern <code class="regex rouge"><span class="pcre2-semantic">(a|(z))(bc)</span></code> the return from the function
is 4, and groups 1 and 3 are matched, but 2 is not. When this happens, both
values in the offset pairs corresponding to unused groups are set to
<code class="constant pcre2-api rouge"><span class="no">PCRE2_UNSET</span></code>.</p>
<p>Offset values that correspond to unused groups at the end of the expression are
also set to <code class="constant pcre2-api rouge"><span class="no">PCRE2_UNSET</span></code>. For example, if the string <code class="subject rouge"><span class="pcre2-semantic">abc</span></code> is matched against
the pattern <code class="regex rouge"><span class="pcre2-semantic">(abc)(x(yz)?)?</span></code> groups 2 and 3 are not matched. The return from the
function is 2, because the highest used capture group number is 1. The offsets
for the second and third capture groups (assuming the vector is large enough,
of course) are set to <code class="constant pcre2-api rouge"><span class="no">PCRE2_UNSET</span></code>.</p>
<p>Elements in the ovector that do not correspond to capturing parentheses in the
pattern are never changed. That is, if a pattern contains <em>n</em> capturing
parentheses, no more than <code class="c rouge" data-lang="c"><span class="nv">ovector</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span></code> to <code class="c rouge" data-lang="c"><span class="nv">ovector</span><span class="p">[</span><span class="mi">2</span><em><span class="nv">n</span></em><span class="o">+</span><span class="mi">1</span><span class="p">]</span></code> are set by
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>. The other elements retain whatever values they previously
had. After a failed match attempt, the contents of the ovector are unchanged.</p></section>
<section class="doc-section level-1"><h2 id="other-match-information">Other information about a match</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">PCRE2_SPTR</span> <span class="nf">pcre2_get_mark</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">PCRE2_SIZE</span> <span class="nf">pcre2_get_startchar</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">);</span>
<span class="kt">PCRE2_SPTR</span> <span class="nf">pcre2_get_subject</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">lengthptr</span><span class="p">);</span></code></pre></div>
<p>As well as the offsets in the ovector, other information about a match is
retained in the match data block and can be retrieved by the above functions in
appropriate circumstances. If they are called at other times, the result is
undefined.</p>
<p>After a successful match, a partial match (<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code>), or a
failure to match (<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code>), <code class="function pcre2-api rouge"><span class="nf">pcre2_get_subject()</span></code> returns
the subject pointer that was passed to the matching function. For a successful
match with <code class="constant pcre2-api rouge"><span class="no">PCRE2_COPY_MATCHED_SUBJECT</span></code>, it returns a pointer to a copy of
the subject that is owned by the match data block instead (except for
<code class="function pcre2-api rouge"><span class="nf">pcre2_jit_match()</span></code> which ignores <code class="constant pcre2-api rouge"><span class="no">PCRE2_COPY_MATCHED_SUBJECT</span></code>). The copy
is exactly the same length as the subject that was passed to the matching
function and is additionally zero-terminated. The copy is freed when the match
data block is reused for another match or is freed. If there is any match error
other than <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code> or <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code>,
<code class="function pcre2-api rouge"><span class="nf">pcre2_get_subject()</span></code> may return <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>. If the <code class="parameter pcre2-api rouge"><span class="nv">lengthptr</span></code> argument
is not <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, it receives the length in code units of the string which is
returned, excluding the terminating zero (the subject string may contain
embedded NUL characters).</p>
<p>After a successful match, a partial match (<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code>), or a failure
to match (<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code>), a mark name may be available. The function
<code class="function pcre2-api rouge"><span class="nf">pcre2_get_mark()</span></code> can be called to access this name, which can be
specified in the pattern by any of the backtracking control verbs, not just
<code class="regex rouge"><span class="pcre2-semantic">(*MARK)</span></code>. The same function applies to all the verbs. It returns a pointer to
the zero-terminated name, which is within the compiled pattern. If no name is
available, <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> is returned. The length of the name (excluding the terminating
zero) is stored in the code unit that precedes the name. You should use this
length instead of relying on the terminating zero if the name might contain a
binary zero.</p>
<p>After a successful match, the name that is returned is the last mark name
encountered on the matching path through the pattern. Instances of backtracking
verbs without names do not count. Thus, for example, if the matching path
contains <code class="regex rouge"><span class="pcre2-semantic">(*MARK:A)(*PRUNE)</span></code>, the name <code class="regex rouge"><span class="pcre2-semantic">A</span></code> is returned. After a "no match" or a
partial match, the last encountered name is returned. For example, consider
this pattern:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">^(*MARK:A)((*MARK:B)a|b)c</span></code></pre></div>
<p>When it matches <code class="subject rouge"><span class="pcre2-semantic">bc</span></code>, the returned name is <code class="regex rouge"><span class="pcre2-semantic">A</span></code>. The <code class="regex rouge"><span class="pcre2-semantic">B</span></code> mark is "seen" in the first
branch of the group, but it is not on the matching path. On the other hand,
when this pattern fails to match <code class="subject rouge"><span class="pcre2-semantic">bx</span></code>, the returned name is <code class="regex rouge"><span class="pcre2-semantic">B</span></code>.</p>
<section class="admonition-block warning" role="doc-notice"><h6 class="block-title label-only"><span class="title-label">Warning: </span></h6><p>By default, certain start-of-match optimizations are used to
give a fast "no match" result in some situations. For example, if the anchoring
is removed from the pattern above, there is an initial check for the presence
of <code class="subject rouge"><span class="pcre2-semantic">c</span></code> in the subject before running the matching engine. This check fails for
<code class="subject rouge"><span class="pcre2-semantic">bx</span></code>, causing a match failure without seeing any marks. You can disable the
start-of-match optimizations by setting the <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_START_OPTIMIZE</span></code> option for
<code class="function pcre2-api rouge"><span class="nf">pcre2_compile()</span></code> or by starting the pattern with <code class="regex rouge"><span class="pcre2-semantic">(*NO_START_OPT)</span></code>.</p></section>
<p>After a successful match, a partial match, or one of the invalid UTF errors
(for example, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UTF8_ERR5</span></code>), <code class="function pcre2-api rouge"><span class="nf">pcre2_get_startchar()</span></code> can be
called. After a successful or partial match it returns the code unit offset of
the character at which the match started. For a non-partial match, this can be
different to the value of <code class="c rouge" data-lang="c"><span class="nv">ovector</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span></code> if the pattern contains the <code class="regex rouge"><span class="pcre2-semantic">\K</span></code>
escape sequence. After a partial match, however, this value is always the same
as <code class="c rouge" data-lang="c"><span class="nv">ovector</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span></code> because <code class="regex rouge"><span class="pcre2-semantic">\K</span></code> does not affect the result of a partial match.</p>
<p>After a UTF check failure, <code class="function pcre2-api rouge"><span class="nf">pcre2_get_startchar()</span></code> can be used to obtain
the code unit offset of the invalid UTF character. Details are given in the
<a href="./pcre2unicode.html"><code>pcre2unicode</code></a>
page.</p></section>
<section class="doc-section level-1"><h2 id="_error_returns_from_pcre2_match">Error returns from <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code></h2><p>If <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> fails, it returns a negative number. This can be
converted to a text string by calling the <code class="function pcre2-api rouge"><span class="nf">pcre2_get_error_message()</span></code>
function (see "Obtaining a textual error message"
below).
Negative error codes are also returned by other functions, and are documented
with them. The codes are given names in the header file. If UTF checking is in
force and an invalid UTF subject string is detected, one of a number of
UTF-specific negative error codes is returned. Details are given in the
<a href="./pcre2unicode.html"><code>pcre2unicode</code></a>
page. The following are the other errors that may be returned by
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>:</p>
<dl class="errors compact" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code></span></dt><dd>The subject string did not match the pattern.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code></span></dt><dd>The subject string did not match, but it did match partially. See the
<a href="./pcre2partial.html"><code>pcre2partial</code></a>
documentation for details of partial matching.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADMAGIC</span></code></span></dt><dd>PCRE2 stores a 4-byte "magic number" at the start of the compiled code, to
catch the case when it is passed a junk pointer. This is the error that is
returned when the magic number is not present.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADMODE</span></code></span></dt><dd>This error is given when a compiled pattern is passed to a function in a
library of a different code unit width, for example, a pattern compiled by
the 8-bit library is passed to a 16-bit or 32-bit library function.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOFFSET</span></code></span></dt><dd>The value of <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> was greater than the length of the subject.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOFFSETLIMIT</span></code></span></dt><dd>A non-default offset limit was set without compiling the pattern with
<code class="constant pcre2-api rouge"><span class="no">PCRE2_USE_OFFSET_LIMIT</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOFFSETLIMITVALUE</span></code></span></dt><dd>The offset limit in the match context was greater than the length of the
subject and was not <code class="constant pcre2-api rouge"><span class="no">PCRE2_UNSET</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOPTION</span></code></span></dt><dd>An unrecognized bit was set in the <code class="parameter pcre2-api rouge"><span class="nv">options</span></code> argument.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADUTFOFFSET</span></code></span></dt><dd>The UTF code unit sequence that was passed as a subject was checked and found
to be valid (the <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code> option was not set), but the value of
<code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> did not point to the beginning of a UTF character or the end
of the subject.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_CALLOUT</span></code></span></dt><dd>This error is never generated by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> itself. It is provided for
use by callout functions that want to cause <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> or
<code class="function pcre2-api rouge"><span class="nf">pcre2_callout_enumerate()</span></code> to return a distinctive error code. See the
<a href="./pcre2callout.html"><code>pcre2callout</code></a>
documentation for details.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_DEPTHLIMIT</span></code></span></dt><dd>The nested backtracking depth limit was reached.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_HEAPLIMIT</span></code></span></dt><dd>The heap limit was reached.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_INTERNAL</span></code></span></dt><dd>An unexpected internal error has occurred. This error could be caused by a bug
in PCRE2 or by overwriting of the compiled pattern.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_JIT_STACKLIMIT</span></code></span></dt><dd>This error is returned when a pattern that was successfully studied using JIT
is being matched, but the memory available for the just-in-time processing
stack is not large enough. See the
<a href="./pcre2jit.html"><code>pcre2jit</code></a>
documentation for more details.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_MATCHLIMIT</span></code></span></dt><dd>The backtracking match limit was reached.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMEMORY</span></code></span></dt><dd>Heap memory is used to remember backtracking points. This error is given when
the memory allocation function (default or custom) fails. Note that a different
error, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_HEAPLIMIT</span></code>, is given if the amount of memory needed exceeds
the heap limit. <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMEMORY</span></code> is also returned if
<code class="constant pcre2-api rouge"><span class="no">PCRE2_COPY_MATCHED_SUBJECT</span></code> is set and memory allocation fails.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NULL</span></code></span></dt><dd>Either the <code class="parameter pcre2-api rouge"><span class="nv">code</span></code>, <code class="parameter pcre2-api rouge"><span class="nv">subject</span></code>, or <code class="parameter pcre2-api rouge"><span class="nv">match_data</span></code> argument was passed
as <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_RECURSELOOP</span></code></span></dt><dd>This error is returned when <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> detects a recursion loop within
the pattern. Specifically, it means that either the whole pattern or a
capture group has been called recursively for the second time at the same
position in the subject string. Some simple patterns that might do this are
detected and faulted at compile time, but more complicated cases, in particular
mutual recursions between two different groups, cannot be detected until
matching is attempted.</dd></div></dl></section>
<section class="doc-section level-1"><h2 id="_obtaining_a_textual_error_message">Obtaining a textual error message</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_get_error_message</span><span class="p">(</span><span class="kt">int</span> <span class="nv">errorcode</span><span class="p">,</span> <span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">buffer</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">bufflen</span><span class="p">);</span></code></pre></div>
<p>A text message for an error code from any PCRE2 function (compile, match, or
auxiliary) can be obtained by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_get_error_message()</span></code>. The code
is passed as the first argument, with the remaining two arguments specifying a
code unit buffer and its length in code units, into which the text message is
placed. The message is returned in code units of the appropriate width for the
library that is being used. An error code of zero is also recognized.</p>
<p>The returned message is terminated with a trailing zero, and the function
returns the number of code units used, excluding the trailing zero. If the
error number is unknown, the negative error code <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADDATA</span></code> is
returned without changing the buffer, even when <code class="parameter pcre2-api rouge"><span class="nv">bufflen</span></code> is zero.
If the buffer is too small, the message is truncated (but still with
a trailing zero, assuming <code class="parameter pcre2-api rouge"><span class="nv">bufflen</span></code> is not zero), and the negative error code
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMEMORY</span></code> is returned.
With a recognized code and zero capacity, no output is written. The buffer
pointer may be <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> only when its capacity is zero.
None of the messages is very long; a buffer size of 120 code units is ample.</p>
<p>No arithmetic (including unary negation) should ever be performed on error codes
by clients. For any PCRE2 function that returns error codes, that code should be
handled as-is.</p></section>
<section class="doc-section level-1"><h2 id="iterating-over-matches">Iterating over all matches</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_next_match</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">pstart_offset</span><span class="p">,</span> <span class="kt">uint32_t</span> <span class="p">*</span><span class="nv">poptions</span><span class="p">);</span></code></pre></div>
<p>A common task for applications is to implement "global" matching behaviour,
for example, replacing all matches in the subject; splitting the subject on all
matches; or simply counting the number of matches. The <code class="function pcre2-api rouge"><span class="nf">pcre2_next_match()</span></code>
function helps with this task by providing the appropriate parameters for the
next match attempt (available since PCRE2 10.47).</p>
<p>First, a match attempt should be made using one of the matching functions
(<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, or <code class="function pcre2-api rouge"><span class="nf">pcre2_jit_match()</span></code>).
Then, <code class="function pcre2-api rouge"><span class="nf">pcre2_next_match()</span></code> can be called, providing the same
<code class="parameter pcre2-api rouge"><span class="nv">match_data</span></code> parameter.</p>
<p>It returns 0 ("false") if there is no need to make a further match attempt, or
1 ("true") if another match should be attempted. Returning 1 does not imply that
there is another match, only that another match should be attempted (which may
return <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code>).</p>
<p>The <code class="c rouge" data-lang="c"><span class="p">*</span><span class="nv">pstart_offset</span></code> and <code class="c rouge" data-lang="c"><span class="p">*</span><span class="nv">poptions</span></code> are set if the function returns 1.
The <code class="c rouge" data-lang="c"><span class="p">*</span><span class="nv">pstart_offset</span></code> should be passed to the next match attempt directly,
and the <code class="c rouge" data-lang="c"><span class="p">*</span><span class="nv">poptions</span></code> should be passed to the next match attempt by combining
with the application’s match options using OR.</p>
<p>There is some code that demonstrates how to do this in the
<a href="./pcre2demo.html"><code>pcre2demo</code></a>
sample program. The general pattern is:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="kt">uint32_t</span> <span class="nv">app_options</span> <span class="o">=</span> <span class="p">...;</span>
<span class="kt">uint32_t</span> <span class="nv">global_options</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">start_offset</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<span class="k">while</span> <span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="p">{</span>
<span class="kt">int</span> <span class="nv">rc</span> <span class="o">=</span> <span class="nf">pcre2_match</span><span class="p">(</span><span class="nv">re</span><span class="p">,</span> <span class="nv">subject</span><span class="p">,</span> <span class="nv">subject_len</span><span class="p">,</span> <span class="nv">start_offset</span><span class="p">,</span>
<span class="nv">app_options</span> <span class="o">|</span> <span class="nv">global_options</span><span class="p">,</span> <span class="nv">match_data</span><span class="p">,</span>
<span class="nv">match_context</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="nv">rc</span> <span class="o">==</span> <span class="no">PCRE2_ERROR_NOMATCH</span><span class="p">)</span>
<span class="k">break</span><span class="p">;</span> <span class="cm">/* no match, and no more attempts */</span>
<span class="k">if</span> <span class="p">(</span><span class="nv">rc</span> <span class="o">&lt;</span> <span class="mi">0</span><span class="p">)</span>
<span class="p">{</span> <span class="cm">/* ... exit */</span> <span class="p">}</span>
<span class="cm">/* ...handle the match */</span>
<span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="nf">pcre2_next_match</span><span class="p">(</span><span class="nv">match_data</span><span class="p">,</span> <span class="p">&amp;</span><span class="nv">start_offset</span><span class="p">,</span> <span class="p">&amp;</span><span class="nv">global_options</span><span class="p">))</span>
<span class="k">break</span><span class="p">;</span> <span class="cm">/* no more attempts */</span>
<span class="p">}</span></code></pre></div>
<p>The guarantees provided by <code class="function pcre2-api rouge"><span class="nf">pcre2_next_match()</span></code> are that the <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code>
will advance, so the loop will definitely terminate. The conditions which
ensure this are that either:</p>
<ol class="loweralpha compact" type="a"><li><code class="function pcre2-api rouge"><span class="nf">pcre2_next_match()</span></code> returns 0 (false); or</li><li>the returned <code class="c rouge" data-lang="c"><span class="p">*</span><span class="nv">pstart_offset</span></code> is strictly greater than the previous
<code class="c rouge" data-lang="c"><span class="nv">start_offset</span></code>; or</li><li>if the previous match was a successful match of the empty string, the returned
<code class="c rouge" data-lang="c"><span class="p">*</span><span class="nv">pstart_offset</span></code> is equal to the previous <code class="c rouge" data-lang="c"><span class="nv">ovector</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span></code>, and <code class="c rouge" data-lang="c"><span class="p">*</span><span class="nv">poptions</span></code>
will be set to <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEMPTY_ATSTART</span></code> to prevent another empty match from
being returned.</li></ol>
<p>A loop implemented as shown above will always terminate, unless there is a bug
in PCRE2. As a measure of "defensive programming", applications are encouraged
to add an assertion or check to break their loop if it does not make progress
(and report the issue as a bug).</p>
<p>If an application does not use the flag <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK</span></code>, then
each match is "well-behaved" and satisfies:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="nv">start_offset</span> <span class="o">&lt;=</span> <span class="nv">ovector</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">&lt;=</span> <span class="nv">ovector</span><span class="p">[</span><span class="mi">1</span><span class="p">].</span></code></pre></div>
<p>In this case, the matches found by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> with <code class="function pcre2-api rouge"><span class="nf">pcre2_next_match()</span></code> will be
sorted, non-overlapping (possibly touching), and with no duplicates.</p>
<p>Otherwise, if <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK</span></code> is used, then the guarantees are
considerably weaker. We do not guarantee that the matches will always advance:
only that the <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> will. The matches found by <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> with
<code class="function pcre2-api rouge"><span class="nf">pcre2_next_match()</span></code> will be a finite sequence (as <code class="function pcre2-api rouge"><span class="nf">pcre2_next_match()</span></code> ensures that
<code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> advances, so the search will terminate). The matches can however be
overlapping, can contain duplicates, and (in truly pathological examples) may
not even be sorted by <code class="c rouge" data-lang="c"><span class="nv">ovector</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span></code>. Additionally, each match itself can end before
it starts (<code class="c rouge" data-lang="c"><span class="nv">ovector</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">&lt;</span> <span class="nv">ovector</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span></code>). We recommend that applications do not set
<code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK</span></code>.</p></section>
<section class="doc-section level-1"><h2 id="_extracting_captured_substrings_by_number">Extracting captured substrings by number</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_substring_length_bynumber</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">stringnumber</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_copy_bynumber</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">stringnumber</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">buffer</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_get_bynumber</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">stringnumber</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="p">*</span><span class="nv">stringptr</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_substring_free</span><span class="p">(</span><span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">string</span><span class="p">);</span></code></pre></div>
<p>Captured substrings can be accessed directly by using the ovector as described
above.
For convenience, auxiliary functions are provided for extracting captured
substrings as new, separate, zero-terminated strings. A substring that contains
a binary zero is correctly extracted and has a further zero added on the end,
but the result is not, of course, a C string.</p>
<p>The functions in this section identify substrings by number. The number zero
refers to the entire matched substring, with higher numbers referring to
substrings captured by parenthesized groups. After a partial match, only
substring zero is available. An attempt to extract any other substring gives
the error <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code>. The section
<a href="#extracting-substrings-by-name">Extracting a list of all captured substrings</a> describes similar functions for
extracting captured substrings by name.</p>
<p>If a pattern uses the <code class="regex rouge"><span class="pcre2-semantic">\K</span></code> escape sequence within a positive lookahead assertion,
the reported start of a successful match can be greater than the end of the
match. For example, if the pattern <code class="regex rouge"><span class="pcre2-semantic">(?=ab\K)</span></code> is matched against <code class="subject rouge"><span class="pcre2-semantic">ab</span></code>, the start
and end offset values for the match are 2 and 0. In this situation, calling
these functions with a zero substring number extracts a zero-length empty
string.</p>
<p>You can find the length in code units of a captured substring without
extracting it by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_length_bynumber()</span></code>. The first
argument is a pointer to the match data block, the second is the group number,
and the third is a pointer to a variable into which the length is placed. If
you just want to know whether or not the substring has been captured, you can
pass the third argument as <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>.</p>
<p>The <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_copy_bynumber()</span></code> function copies a captured substring
into a supplied buffer, whereas <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_get_bynumber()</span></code> copies it
into new memory, obtained using the same memory allocation function that was
used for the match data block. The first two arguments of these functions are a
pointer to the match data block and a capture group number.</p>
<p>The final arguments of <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_copy_bynumber()</span></code> are a pointer to
the buffer and a pointer to a variable that contains its length in code units.
This is updated to contain the actual number of code units used for the
extracted substring, excluding the terminating zero.</p>
<p>For <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_get_bynumber()</span></code> the third and fourth arguments point
to variables that are updated with a pointer to the new memory and the number
of code units that comprise the substring, again excluding the terminating
zero. When the substring is no longer needed, the memory should be freed by
calling <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_free()</span></code>.</p>
<p>The return value from all these functions is zero for success, or a negative
error code. If the pattern match failed, the match failure code is returned.
If a substring number greater than zero is used after a partial match,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code> is returned. Other possible error codes are:</p>
<dl class="compact" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMEMORY</span></code></span></dt><dd>The buffer was too small for <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_copy_bynumber()</span></code>, or the
attempt to get memory failed for <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_get_bynumber()</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOSUBSTRING</span></code></span></dt><dd>There is no substring with that number in the pattern, that is, the number is
greater than the number of capturing parentheses.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNAVAILABLE</span></code></span></dt><dd>The substring number, though not greater than the number of captures in the
pattern, is greater than the number of slots in the ovector, so the substring
could not be captured.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNSET</span></code></span></dt><dd>The substring did not participate in the match. For example, if the pattern is
<code class="regex rouge"><span class="pcre2-semantic">(abc)|(def)</span></code> and the subject is <code class="subject rouge"><span class="pcre2-semantic">def</span></code>, and the ovector contains at least two
capturing slots, substring number 1 is unset.</dd></div></dl></section>
<section class="doc-section level-1"><h2 id="extracting-substrings-by-name">Extracting a list of all captured substrings</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_substring_list_get</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="p">*</span><span class="p">*</span><span class="nv">listptr</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="p">*</span><span class="nv">lengthsptr</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_substring_list_free</span><span class="p">(</span><span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="p">*</span><span class="nv">list</span><span class="p">);</span></code></pre></div>
<p>The <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_list_get()</span></code> function extracts all available substrings
and builds a list of pointers to them. It also (optionally) builds a second
list that contains their lengths (in code units), excluding a terminating zero
that is added to each of them. All this is done in a single block of memory
that is obtained using the same memory allocation function that was used to get
the match data block.</p>
<p>This function must be called only after a successful match. If called after a
partial match, the error code <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code> is returned.</p>
<p>The address of the memory block is returned via <code class="parameter pcre2-api rouge"><span class="nv">listptr</span></code>, which is also
the start of the list of string pointers. The end of the list is marked by a
<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> pointer. The address of the list of lengths is returned via
<code class="parameter pcre2-api rouge"><span class="nv">lengthsptr</span></code>. If your strings do not contain binary zeros and you do not
therefore need the lengths, you may supply <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> as the <code class="parameter pcre2-api rouge"><span class="nv">lengthsptr</span></code>
argument to disable the creation of a list of lengths. The yield of the
function is zero if all went well, or <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMEMORY</span></code> if the memory block
could not be obtained. When the list is no longer needed, it should be freed by
calling <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_list_free()</span></code>.</p>
<p>If this function encounters a substring that is unset, which can happen when
capture group number <em>n+1</em> matches some part of the subject, but group
<em>n</em> has not been used at all, it returns an empty string. This can be
distinguished from a genuine zero-length substring by inspecting the
appropriate offset in the <code class="parameter pcre2-api rouge"><span class="nv">ovector</span></code>, which contain <code class="constant pcre2-api rouge"><span class="no">PCRE2_UNSET</span></code> for unset
substrings, or by calling <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_length_bynumber()</span></code>.</p></section>
<section class="doc-section level-1"><h2 id="_extracting_captured_substrings_by_name">Extracting captured substrings by name</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_substring_number_from_name</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_length_byname</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_copy_byname</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">buffer</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">int</span> <span class="nf">pcre2_substring_get_byname</span><span class="p">(</span><span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="p">*</span><span class="nv">stringptr</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">sizeptr</span><span class="p">);</span>
<span class="kt">void</span> <span class="nf">pcre2_substring_free</span><span class="p">(</span><span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">string</span><span class="p">);</span></code></pre></div>
<p>To extract a substring by name, you first have to find associated number.
For example, for this pattern:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">(a+)b(?&lt;xxx&gt;\d+)...</span></code></pre></div>
<p>the number of the capture group called "xxx" is 2. If the name is known to be
unique (<code class="constant pcre2-api rouge"><span class="no">PCRE2_DUPNAMES</span></code> was not set), you can find the number from the name by
calling <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_number_from_name()</span></code>. The first argument is the
compiled pattern, and the second is the name. The yield of the function is the
group number, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOSUBSTRING</span></code> if there is no group with that name, or
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOUNIQUESUBSTRING</span></code> if there is more than one group with that name.
Given the number, you can extract the substring directly from the ovector, or
use one of the "bynumber" functions described above.</p>
<p>For convenience, there are also "byname" functions that correspond to the
"bynumber" functions, the only difference being that the second argument is a
name instead of a number. If <code class="constant pcre2-api rouge"><span class="no">PCRE2_DUPNAMES</span></code> is set and there are duplicate
names, these functions scan all the groups with the given name, and return the
captured substring from the first named group that is set.</p>
<p>If there are no groups with the given name, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOSUBSTRING</span></code> is
returned. If all groups with the name have numbers that are greater than the
number of slots in the ovector, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNAVAILABLE</span></code> is returned. If there
is at least one group with a slot in the ovector, but no group is found to be
set, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNSET</span></code> is returned.</p>
<section class="admonition-block warning" role="doc-notice"><h6 class="block-title label-only"><span class="title-label">Warning: </span></h6><p>If the pattern uses the <code class="regex rouge"><span class="pcre2-semantic">(?|</span></code> feature to set up multiple
capture groups with the same number, as described in the
section <a href="./pcre2pattern.html#duplicate-group-numbers">Duplicate group numbers</a>
in the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
page, you cannot use names to distinguish the different capture groups, because
names are not included in the compiled code. The matching process uses only
numbers. For this reason, the use of different names for groups with the
same number causes an error at compile time.</p></section></section>
<section class="doc-section level-1"><h2 id="creating-substitution-string">Creating a new string with substitutions</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_substitute</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">PCRE2_SPTR</span> <span class="nv">subject</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">start_offset</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">replacement</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">rlength</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">buffer</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">blength</span><span class="p">);</span></code></pre></div>
<p>This function optionally calls <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> and then makes a copy of the
subject string in <code class="parameter pcre2-api rouge"><span class="nv">buffer</span></code>, replacing parts that were matched with
the <code class="parameter pcre2-api rouge"><span class="nv">replacement</span></code> string, whose length is supplied in <code class="parameter pcre2-api rouge"><span class="nv">rlength</span></code>, which
can be given as <code class="constant pcre2-api rouge"><span class="no">PCRE2_ZERO_TERMINATED</span></code> for a zero-terminated string. As a
special case, if <code class="parameter pcre2-api rouge"><span class="nv">replacement</span></code> is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> and <code class="parameter pcre2-api rouge"><span class="nv">rlength</span></code> is zero, the
replacement is assumed to be an empty string. If <code class="parameter pcre2-api rouge"><span class="nv">rlength</span></code> is non-zero, an
error occurs if <code class="parameter pcre2-api rouge"><span class="nv">replacement</span></code> is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>.</p>
<p>There is an option (see <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_REPLACEMENT_ONLY</span></code> below) to return just
the replacement string(s). The default action is to perform just one
replacement if the pattern matches, but there is an option that requests
multiple replacements (see <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_GLOBAL</span></code> below).</p>
<p>If successful, <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> returns the number of substitutions
that were carried out. This may be zero if no match was found, and is never
greater than one unless <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_GLOBAL</span></code> is set. A negative value is
returned if an error is detected.</p>
<p>Matches in which a <code class="regex rouge"><span class="pcre2-semantic">\K</span></code> item in a lookahead in the pattern causes the match to
end before it starts are not supported, and give rise to an error return. For
global replacements, matches in which <code class="regex rouge"><span class="pcre2-semantic">\K</span></code> in a lookbehind causes the match to
start earlier than the point that was reached in the previous iteration are
also not supported. (These cases are only possible if the pattern was compiled
with the backwards-compatibility option <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK</span></code>.)</p>
<p>The first seven arguments of <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> are the same as for
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, except that the partial matching options are not
permitted, and <code class="parameter pcre2-api rouge"><span class="nv">match_data</span></code> may be passed as <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, in which case a match
data block is obtained and freed within this function, using memory management
functions from the match context, if provided, or else those that were used to
allocate memory for the compiled code.</p>
<p>If <code class="parameter pcre2-api rouge"><span class="nv">match_data</span></code> is not <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> and <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code> is not set, the
provided block is used for all calls to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, and its contents
afterwards are the result of the final call made internally by
<code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> to the matching function. For global changes, this will
always be a no-match error. The contents of the ovector within the match data
block may or may not have been changed.</p>
<p>As well as the usual options for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, a number of additional
options can be set in the <code class="parameter pcre2-api rouge"><span class="nv">options</span></code> argument of <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code>.
One such option is <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code>. When this is set, an external
<code class="parameter pcre2-api rouge"><span class="nv">match_data</span></code> block must be provided, and it must have already been used for
an external call to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> (or <code class="function pcre2-api rouge"><span class="nf">pcre2_jit_match()</span></code>) with the
same pattern, subject pointer, effective subject length, start offset, and match
option arguments (substitute-specific options can be added to the <code class="parameter pcre2-api rouge"><span class="nv">options</span></code>
argument). If any of these parameters is changed, <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code>
returns an error. The data in the <code class="parameter pcre2-api rouge"><span class="nv">match_data</span></code> block (return code, offset
vector) is used for the first substitution instead of calling
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> from within <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code>. This allows an
application to check for a match before choosing to substitute, without having
to repeat the match.</p>
<p>If the contents of the subject buffer are mutated in between <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>
and a call to <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> with <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code>, the
behaviour is unsafe; in particular, in this case, PCRE2 is unable to ensure that
the offsets in the ovector point to the start of characters (with UTF-encoded
input).</p>
<p>The contents of the externally supplied match data block are not changed when
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code> is set, and so the match block is permitted for use in
another call using <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code>. If <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_GLOBAL</span></code> is also
set, <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> is called after the first substitution to check for
furthe matches, but this is done using an internally obtained match data block,
thus always leaving the external block unchanged.</p>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">code</span></code> argument is not used for matching before the first substitution
when <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code> is set, but it must be provided, even when
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_GLOBAL</span></code> is not set, because it contains information such as the
UTF setting and the number of capturing parentheses in the pattern.</p>
<p>When using <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code>, you should not modify the subject string
in between the prior call to <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> and <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code>,
as the substitution assumes that the passed-in ovector is compatible with the
subject string. Although PCRE2 does verify that the subject is a pointer to the
same buffer, it cannot in general verify whether the contents of the buffer have
changed. For example, if the subject buffer is mutated from one valid UTF-8
string to another valid string, of the same length in code units, the ovector
offsets are no longer guaranteed to point to the start of a character. Beware
that with <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code> in UTF mode, the subject string is not
re-scanned for UTF validity when <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> first uses it.</p>
<p>The default action of <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> is to return a copy of the
subject string with matched substrings replaced. However, if
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_REPLACEMENT_ONLY</span></code> is set, only the replacement substrings are
returned. In the global case, multiple replacements are concatenated in the
output buffer. Substitution callouts (see
below)
can be used to separate them if necessary.</p>
<p>Partial matching is supported, with limitations: if matching succeeds but with a
partial match, then <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> returns <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code>. When
partial-matching (either of <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_HARD</span></code> or <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_SOFT</span></code> is passed),
then <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_REPLACEMENT_ONLY</span></code> must also be set, or else
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADOPTION</span></code> is returned. Similarly, certain replacement items
(<code class="repl rouge"><span class="pcre2-semantic">$'</span></code> and <code class="repl rouge"><span class="pcre2-semantic">$_</span></code>) cause <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIALSUBS</span></code> to be returned when partial-matching,
even if a complete match is found.</p>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">blength</span></code> argument of <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> must point to a
variable that contains the length, in code units, of the output buffer. If the
function is successful, the value is updated to contain the length in code
units of the new string, excluding the trailing zero that is automatically
added.</p>
<p>If the function is not successful, the value set via <code class="parameter pcre2-api rouge"><span class="nv">blength</span></code> depends
on the type of error. For syntax errors in the replacement string, the value is
the offset in the replacement string where the error was detected. For other
errors, the value is <code class="constant pcre2-api rouge"><span class="no">PCRE2_UNSET</span></code> by default. This includes the case of the
output buffer being too small, unless <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_OVERFLOW_LENGTH</span></code> is set.</p>
<p><code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_OVERFLOW_LENGTH</span></code> changes what happens when the output buffer is
too small. The default action is to return <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMEMORY</span></code> immediately. If
this option is set, however, <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> continues to go through
the motions of matching and substituting (without, of course, writing anything)
in order to compute the size of buffer that is needed, which will include the
extra space for the terminating NUL. This value is passed back via the
<code class="parameter pcre2-api rouge"><span class="nv">blength</span></code> variable, with the result of the function still being
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMEMORY</span></code>.</p>
<p>Passing a buffer size of zero (with <code class="parameter pcre2-api rouge"><span class="nv">buffer</span></code> optionally <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>) is a
permitted way of finding out how much memory is needed for given substitution.
However, this does mean that the entire operation is carried out twice.
Depending on the application, it may be more efficient to allocate a large
buffer and free the excess afterwards, instead of using
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_OVERFLOW_LENGTH</span></code>.</p>
<p>The replacement string, which is interpreted as a UTF string in UTF mode, is
checked for UTF validity unless <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code> is set. An invalid UTF
replacement string causes an immediate return with the relevant UTF error code.</p>
<p>If <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_LITERAL</span></code> is set, the replacement string is not interpreted
in any way. By default, however, a dollar character is an escape character that
can specify the insertion of characters from capture groups and names from
<code class="regex rouge"><span class="pcre2-semantic">(*MARK)</span></code> or other control verbs in the pattern. Dollar is the only escape
character (backslash is treated as literal). The following forms are
recognized:</p>
<dl class="compact" style="--tab-width: 10"><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">$$</span></code></span></dt><dd>Insert a dollar character</dd></div><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">$<em>n</em></span></code> or <code class="repl rouge"><span class="pcre2-semantic">${<em>n</em>}</span></code></span></dt><dd>Insert the contents of group <em>n</em></dd></div><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">$&lt;<em>name</em>&gt;</span></code></span></dt><dd>Insert the contents of named group</dd></div><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">$0</span></code> or <code class="repl rouge"><span class="pcre2-semantic">$&amp;</span></code></span></dt><dd>Insert the entire matched substring</dd></div><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">$`</span></code></span></dt><dd>Insert the substring that precedes the match</dd></div><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">$'</span></code></span></dt><dd>Insert the substring that follows the match</dd></div><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">$_</span></code></span></dt><dd>Insert the entire input string</dd></div><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">$+</span></code></span></dt><dd>Insert the highest-numbered capture group which matched</dd></div><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">$*MARK</span></code> or <code class="repl rouge"><span class="pcre2-semantic">${*MARK}</span></code></span></dt><dd>Insert a control verb name</dd></div></dl>
<p>Either a group number or a group name can be given for <em>n</em>, for example <code class="repl rouge"><span class="pcre2-semantic">$2</span></code>
or <code class="repl rouge"><span class="pcre2-semantic">$NAME</span></code>. Curly brackets are required only if the following character would be
interpreted as part of the number or name. The number may be zero to include
the entire matched string. For example, if the pattern <code class="regex rouge"><span class="pcre2-semantic">a(b)c</span></code> is matched with
<code class="subject rouge"><span class="pcre2-semantic">=abc=</span></code> and the replacement string <code class="repl rouge"><span class="pcre2-semantic">+$1$0$1+</span></code>, the result is <code class="repl rouge"><span class="pcre2-semantic">=+babcb+=</span></code>.</p>
<p>The JavaScript form <code class="repl rouge"><span class="pcre2-semantic">$&lt;<em>name</em>&gt;</span></code>, where the angle brackets are part of the syntax,
is also recognized for group names, but not for group numbers or <code class="repl rouge"><span class="pcre2-semantic">*MARK</span></code>.</p>
<p><code class="repl rouge"><span class="pcre2-semantic">$*MARK</span></code> inserts the name from the last encountered backtracking control verb on
the matching path that has a name. <code class="regex rouge"><span class="pcre2-semantic">(*MARK)</span></code> must always include a name, but the
other verbs need not. For example, in the case of <code class="regex rouge"><span class="pcre2-semantic">(*MARK:A)(*PRUNE)</span></code> the name
inserted is <code class="repl rouge"><span class="pcre2-semantic">A</span></code>, but for <code class="regex rouge"><span class="pcre2-semantic">(*MARK:A)(*PRUNE:B)</span></code> the relevant name is <code class="repl rouge"><span class="pcre2-semantic">B</span></code>. This
facility can be used to perform simple simultaneous substitutions, as this
<code>pcre2test</code> example shows:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="text">/(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK}
apple lemon
2: pear orange</code></pre></div>
<p><code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_GLOBAL</span></code> causes the function to iterate over the subject string,
replacing every matching substring. If this option is not set, only the first
matching substring is replaced. The search for matches takes place in the
original subject string (that is, previous replacements do not affect it).
Iteration is implemented by advancing the <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> value for each
search, which is always passed the entire subject string. If an offset limit is
set in the match context, searching stops when that limit is reached.</p>
<p>Because global substitutions apply the pattern repeatedly to the subject string,
and always iterate over non-overlapping matches, the substitutions done by
<code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> do not match and substitute text inside the replacement
strings themselves (no recursive/iterative substitution). However, applications
can easily implement other alternative replacement strategies, such as
iteratively replacing, then matching and replacing on the result. The
replacement loop inside <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> is simple and can be emulated
in client code by allocating a buffer, searching for matches in a loop, and
calling <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> with <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_REPLACEMENT_ONLY</span></code> an
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code>, and without <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_GLOBAL</span></code>.</p>
<p>You can restrict the effect of a global substitution to a portion of the
subject string by setting either or both of <code class="parameter pcre2-api rouge"><span class="nv">start_offset</span></code> and an offset
limit. Here is a <code>pcre2test</code> example:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="text">/B/g,replace=!,use_offset_limit
ABC ABC ABC ABC\=offset=3,offset_limit=12
2: ABC A!C A!C ABC</code></pre></div>
<p>When continuing with global substitutions after matching a substring with zero
length, an attempt to find a non-empty match at the same offset is performed.
If this is not successful, the offset is advanced by one character except when
CRLF is a valid newline sequence and the next two characters are CR, LF. In
this case, the offset is advanced by two characters.</p>
<p><code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNKNOWN_UNSET</span></code> causes references to capture groups that do
not appear in the pattern to be treated as unset groups. This option should be
used with care, because it means that a typo in a group name or number no
longer causes the <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOSUBSTRING</span></code> error.</p>
<p><code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNSET_EMPTY</span></code> causes unset capture groups (including unknown
groups when <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNKNOWN_UNSET</span></code> is set) to be treated as empty
strings when inserted as described above. If this option is not set, an attempt
to insert an unset group causes the <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNSET</span></code> error. This option does
not influence the extended substitution syntax described below.</p>
<p><code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_EXTENDED</span></code> causes extra processing to be applied to the
replacement string. Without this option, only the dollar character is special,
and only the group insertion forms listed above are valid. When
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_EXTENDED</span></code> is set, several things change:</p>
<p>Firstly, backslash in a replacement string is interpreted as an escape
character. The usual forms such as <code class="repl rouge"><span class="pcre2-semantic">\x{<em>ddd</em>}</span></code> can be used to specify particular
character codes, and backslash followed by any non-alphanumeric character
quotes that character. Extended quoting can be coded using <code class="repl rouge"><span class="pcre2-semantic">\Q...\E</span></code>, exactly
as in pattern strings. The escapes <code class="repl rouge"><span class="pcre2-semantic">\b</span></code> and <code class="repl rouge"><span class="pcre2-semantic">\v</span></code> are interpreted as the
characters backspace and vertical tab, respectively.</p>
<p>The interpretation of backslash followed by one or more digits is the same as
in a pattern, which in Perl has some ambiguities. Details are given in the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
page.</p>
<p>The Python form <code class="repl rouge"><span class="pcre2-semantic">\g&lt;<em>n</em>&gt;</span></code>, where the angle brackets are part of the syntax and
<em>n</em> is either a group name or number, is recognized as an alternative way
of inserting the contents of a group, for example <code class="repl rouge"><span class="pcre2-semantic">\g&lt;3&gt;</span></code>.</p>
<p>There are also four escape sequences for forcing the case of inserted letters.
Case forcing applies to all inserted characters, including those from capture
groups and letters within <code class="repl rouge"><span class="pcre2-semantic">\Q...\E</span></code> quoted sequences. The insertion mechanism
has three states: no case forcing, force upper case, and force lower case. The
escape sequences change the current state: <code class="repl rouge"><span class="pcre2-semantic">\U</span></code> and <code class="repl rouge"><span class="pcre2-semantic">\L</span></code> change to upper or lower
case forcing, respectively, and <code class="repl rouge"><span class="pcre2-semantic">\E</span></code> (when not terminating a <code class="repl rouge"><span class="pcre2-semantic">\Q</span></code> quoted
sequence) reverts to no case forcing. The sequences <code class="repl rouge"><span class="pcre2-semantic">\u</span></code> and <code class="repl rouge"><span class="pcre2-semantic">\l</span></code> force the next
character (if it is a letter) to upper or lower case, respectively, and then
the state automatically reverts to no case forcing.</p>
<p>However, if <code class="repl rouge"><span class="pcre2-semantic">\u</span></code> is immediately followed by <code class="repl rouge"><span class="pcre2-semantic">\L</span></code> or <code class="repl rouge"><span class="pcre2-semantic">\l</span></code> is immediately followed
by <code class="repl rouge"><span class="pcre2-semantic">\U</span></code>, the next character’s case is forced by the first escape sequence, and
subsequent characters by the second. This provides a "title casing" facility
that can be applied to group captures. For example, if group 1 has captured
<code class="subject rouge"><span class="pcre2-semantic">heLLo</span></code>, the replacement string <code class="repl rouge"><span class="pcre2-semantic">\u\L$1</span></code> becomes <code class="repl rouge"><span class="pcre2-semantic">Hello</span></code>.</p>
<p>If either <code class="constant pcre2-api rouge"><span class="no">PCRE2_UTF</span></code> or <code class="constant pcre2-api rouge"><span class="no">PCRE2_UCP</span></code> was set when the pattern was compiled, Unicode
properties are used for case forcing characters whose code points are greater
than 127. However, only simple case folding, as determined by the Unicode file
<code>CaseFolding.txt</code> is supported. PCRE2 does not support language-specific
special casing rules such as using different lower case Greek sigmas in the
middle and ends of words (as defined in the Unicode file
<code>SpecialCasing.txt</code>).</p>
<p>Note that case forcing sequences such as <code class="repl rouge"><span class="pcre2-semantic">\U...\E</span></code> do not nest. For example,
the result of processing <code class="repl rouge"><span class="pcre2-semantic">\Uaa\LBB\Ecc\E</span></code> is <code class="repl rouge"><span class="pcre2-semantic">AAbbcc</span></code>; the final <code class="repl rouge"><span class="pcre2-semantic">\E</span></code> has no
effect. Note also that the <code class="constant pcre2-api rouge"><span class="no">PCRE2_ALT_BSUX</span></code> and <code class="constant pcre2-api rouge"><span class="no">PCRE2_EXTRA_ALT_BSUX</span></code> options do
not apply to replacement strings.</p>
<p>The final effect of setting <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_EXTENDED</span></code> is to add more
flexibility to capture group substitution. The syntax is similar to that used
by Bash:</p>
<dl class="compact" style="--tab-width: 4"><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">${<em>n</em>:-<em>string</em>}</span></code> </span></dt><dd>insert a default value when group <em>n</em> is unset</dd></div><div class="dlist-item"><dt><span><code class="repl rouge"><span class="pcre2-semantic">${<em>n</em>:+<em>string1</em>:<em>string2</em>}</span></code> </span></dt><dd>insert <em>string1</em> when group <em>n</em> is set, otherwise <em>string2</em></dd></div></dl>
<p>As in the simple case, <em>n</em> may be a group number or a name. The first form
specifies a default value. If group <em>n</em> is set, its value is inserted; if
not, the string is expanded and the result inserted. The second form specifies
strings that are expanded and inserted when group <em>n</em> is set or unset,
respectively. The first form is just a convenient shorthand for</p>
<p><code class="repl rouge"><span class="pcre2-semantic">${<em>n</em>:+${<em>n</em>}:<em>string</em>}</span></code></p>
<p>Backslash can be used to escape colons and closing curly brackets in the
replacement strings. A change of the case forcing state within a replacement
string remains in force afterwards, as shown in this <code>pcre2test</code> example:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="text">/(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo
body
1: hello
somebody
1: HELLO</code></pre></div>
<p>The <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNSET_EMPTY</span></code> option does not affect these extended
substitutions. However, <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNKNOWN_UNSET</span></code> does cause unknown
groups in the extended syntax forms to be treated as unset.</p>
<p>If <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_LITERAL</span></code> is set, <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNKNOWN_UNSET</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNSET_EMPTY</span></code>, and <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_EXTENDED</span></code> are irrelevant and
are ignored.</p>
<section class="doc-section level-2"><h3 id="_substitution_errors">Substitution errors</h3><p>In the event of an error, <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> returns a negative error
code. Except for <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code> (which is never returned), errors from
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> are passed straight back.</p>
<dl class="errors compact" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOSUBSTRING</span></code></span></dt><dd>is returned for a non-existent substring insertion,
unless <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNKNOWN_UNSET</span></code> is set.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNSET</span></code></span></dt><dd>is returned for an unset substring insertion (including an
unknown substring when <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNKNOWN_UNSET</span></code> is set) when the simple
(non-extended) syntax is used and <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_UNSET_EMPTY</span></code> is not set.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMEMORY</span></code></span></dt><dd>is returned if the output buffer is not big enough. If the
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_OVERFLOW_LENGTH</span></code> option is set, the size of buffer that is
needed is returned via <code class="parameter pcre2-api rouge"><span class="nv">blength</span></code>. Note that this does not happen by
default.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NULL</span></code></span></dt><dd>is returned if <code class="parameter pcre2-api rouge"><span class="nv">code</span></code> or <code class="parameter pcre2-api rouge"><span class="nv">blength</span></code> is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>; or if
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_MATCHED</span></code> is set but the <code class="parameter pcre2-api rouge"><span class="nv">match_data</span></code> argument is
<code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>; or if the <code class="parameter pcre2-api rouge"><span class="nv">subject</span></code> or <code class="parameter pcre2-api rouge"><span class="nv">replacement</span></code> or <code class="parameter pcre2-api rouge"><span class="nv">buffer</span></code>
argument is <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>. However, a <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code> <code class="parameter pcre2-api rouge"><span class="nv">replacement</span></code> argument is
allowed if the <code class="parameter pcre2-api rouge"><span class="nv">rlength</span></code> argument is zero; and similarly for <code class="parameter pcre2-api rouge"><span class="nv">subject</span></code>
with zero <code class="parameter pcre2-api rouge"><span class="nv">length</span></code> and <code class="parameter pcre2-api rouge"><span class="nv">buffer</span></code> with zero <code class="parameter pcre2-api rouge"><span class="nv">blength</span></code>.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADMAGIC</span></code></span></dt><dd>the magic number in the compiled code was not recognized.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADMODE</span></code></span></dt><dd>the pattern was compiled for a different code unit width.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADREPLACEMENT</span></code></span></dt><dd>is used for miscellaneous syntax errors in the
replacement string, with more particular errors being <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADREPESCAPE</span></code>
(invalid escape sequence), <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_REPMISSINGBRACE</span></code> (closing curly bracket
not found), <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADSUBSTITUTION</span></code> (syntax error in extended group
substitution), and <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_BADSUBSPATTERN</span></code> (the pattern match ended before
it started or the match started earlier than the current position in the
subject, which can happen if <code class="regex rouge"><span class="pcre2-semantic">\K</span></code> is used in a lookaround assertion).</dd></div></dl>
<p>As for all PCRE2 errors, a text message that describes the error can be
obtained by calling the <code class="function pcre2-api rouge"><span class="nf">pcre2_get_error_message()</span></code> function (see
"Obtaining a textual error message"
above).</p></section>
<section class="doc-section level-2"><h3 id="_substitution_callouts">Substitution callouts</h3><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_substitute_callout</span><span class="p">(</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="kt">int</span> <span class="p">(</span><span class="p">*</span><span class="nv">substitute_callout</span><span class="p">)(</span>
<span class="kt">pcre2_substitute_callout_block</span> <span class="p">*</span><span class="nv">callout_block</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_callout_data</span><span class="p">);</span></code></pre></div>
<p>The <code class="function pcre2-api rouge"><span class="nf">pcre2_set_substitute_callout()</span></code> function can be used to specify a
callout function for <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code>. This information is passed in
a match context. The callout function is called after each substitution has
been processed, but it can cause the replacement not to happen.</p>
<p>The callout function is not called for simulated substitutions that happen as a
result of the <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_OVERFLOW_LENGTH</span></code> option. In this mode, when
substitution processing exceeds the buffer space provided by the caller,
processing continues by counting code units. The simulation is unable to
populate the callout block, and so the simulation is pessimistic about the
required buffer size. Whichever is larger of accepted or rejected substitution
is reported as the required size. Therefore, the returned buffer length may be
an overestimate (without a substitution callout, it is normally an exact
measurement).</p>
<p>The first argument of the callout function is a pointer to a substitute callout
block structure, which contains the following fields, not necessarily in this
order:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="kt">uint32_t</span> <span class="nv">version</span><span class="p">;</span>
<span class="kt">uint32_t</span> <span class="nv">subscount</span><span class="p">;</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">input</span><span class="p">;</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">output</span><span class="p">;</span>
<span class="kt">PCRE2_SIZE</span> <span class="p">*</span><span class="nv">ovector</span><span class="p">;</span>
<span class="kt">uint32_t</span> <span class="nv">oveccount</span><span class="p">;</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">output_offsets</span><span class="p">[</span><span class="mi">2</span><span class="p">];</span></code></pre></div>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">version</span></code> field contains the version number of the block format. The
current version is 0. The version number will increase in future if more fields
are added, but the intention is never to remove any of the existing fields.</p>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">subscount</span></code> field is the number of the current match. It is 1 for the
first callout, 2 for the second, and so on. The <code class="parameter pcre2-api rouge"><span class="nv">input</span></code> and <code class="parameter pcre2-api rouge"><span class="nv">output</span></code>
pointers are copies of the values passed to <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code>.</p>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">ovector</span></code> field points to the ovector, which contains the result of the
most recent match. The <code class="parameter pcre2-api rouge"><span class="nv">oveccount</span></code> field contains the number of pairs that
are set in the ovector, and is always greater than zero.</p>
<p>The <code class="parameter pcre2-api rouge"><span class="nv">output_offsets</span></code> vector contains the offsets of the replacement in the
output string. This has already been processed for dollar and (if requested)
backslash substitutions as described above.</p>
<p>The second argument of the callout function is the value passed as
<code class="parameter pcre2-api rouge"><span class="nv">callout_data</span></code> when the function was registered. The value returned by the
callout function is interpreted as follows:</p>
<p>If the value is zero, the replacement is accepted, and, if
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_GLOBAL</span></code> is set, processing continues with a search for the next
match. If the value is not zero, the current replacement is not accepted. If
the value is greater than zero, processing continues when
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_GLOBAL</span></code> is set. Otherwise (the value is less than zero or
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_GLOBAL</span></code> is not set), the rest of the input is copied to the
output and the call to <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> exits, returning the number of
matches so far.</p></section>
<section class="doc-section level-2"><h3 id="_substitution_case_callouts">Substitution case callouts</h3><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_set_substitute_case_callout</span><span class="p">(</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span>
<span class="nf">PCRE2_SIZE</span> <span class="p">(</span><span class="p">*</span><span class="nv">substitute_case_callout</span><span class="p">)(</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">input</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">input_length</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">output</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">output_capacity</span><span class="p">,</span>
<span class="kt">int</span> <span class="nv">case_operation</span><span class="p">,</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_case_callout_data</span><span class="p">),</span>
<span class="kt">void</span> <span class="p">*</span><span class="nv">substitute_case_callout_data</span><span class="p">);</span></code></pre></div>
<p>The <code class="function pcre2-api rouge"><span class="nf">pcre2_set_substitute_case_callout()</span></code> function can be used to specify
a callout function for <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> to use when performing case
transformations. This does not affect any case insensitivity behaviour when
performing a match, but only the user-visible transformations performed when
processing a substitution such as:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="nf">pcre2_substitute</span><span class="p">(...,</span> <span class="s">"</span><span class="se">\\</span><span class="s">U$1"</span><span class="p">,</span> <span class="p">...)</span></code></pre></div>
<p>The default case transformations applied by PCRE2 are reasonably complete, and,
in UTF or UCP mode, perform the simple locale-invariant case transformations as
specified by Unicode. This is suitable for the internal (invisible)
case-equivalence procedures used during pattern matching, but an application
may wish to use more sophisticated locale-aware processing for the user-visible
substitution transformations.</p>
<p>One example implementation of the <code class="parameter pcre2-api rouge"><span class="nv">substitute_case_callout</span></code> function using the ICU
library would be:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="kt">PCRE2_SIZE</span>
<span class="nf">icu_case_callout</span><span class="p">(</span><span class="kt">PCRE2_SPTR</span> <span class="nv">input</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">input_len</span><span class="p">,</span>
<span class="kt">PCRE2_UCHAR</span> <span class="p">*</span><span class="nv">output</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">output_cap</span><span class="p">,</span>
<span class="kt">int</span> <span class="nv">to_case</span><span class="p">,</span> <span class="kt">void</span> <span class="p">*</span><span class="nv">data_ptr</span><span class="p">)</span>
<span class="p">{</span>
<span class="nv">UErrorCode</span> <span class="nv">err</span> <span class="o">=</span> <span class="no">U_ZERO_ERROR</span><span class="p">;</span>
<span class="kt">int32_t</span> <span class="nv">r</span> <span class="o">=</span>
<span class="nv">to_case</span> <span class="o">==</span> <span class="no">PCRE2_SUBSTITUTE_CASE_LOWER</span>
<span class="o">?</span> <span class="nf">u_strToLower</span><span class="p">(</span><span class="nv">output</span><span class="p">,</span> <span class="nv">output_cap</span><span class="p">,</span> <span class="nv">input</span><span class="p">,</span> <span class="nv">input_len</span><span class="p">,</span>
<span class="kc">NULL</span><span class="p">,</span> <span class="p">&amp;</span><span class="nv">err</span><span class="p">)</span>
<span class="o">:</span> <span class="nv">to_case</span> <span class="o">==</span> <span class="no">PCRE2_SUBSTITUTE_CASE_UPPER</span>
<span class="o">?</span> <span class="nf">u_strToUpper</span><span class="p">(</span><span class="nv">output</span><span class="p">,</span> <span class="nv">output_cap</span><span class="p">,</span> <span class="nv">input</span><span class="p">,</span> <span class="nv">input_len</span><span class="p">,</span>
<span class="kc">NULL</span><span class="p">,</span> <span class="p">&amp;</span><span class="nv">err</span><span class="p">)</span>
<span class="o">:</span> <span class="nf">u_strToTitle</span><span class="p">(</span><span class="nv">output</span><span class="p">,</span> <span class="nv">output_cap</span><span class="p">,</span> <span class="nv">input</span><span class="p">,</span> <span class="nv">input_len</span><span class="p">,</span>
<span class="p">&amp;</span><span class="nv">first_char_only</span><span class="p">,</span> <span class="kc">NULL</span><span class="p">,</span> <span class="p">&amp;</span><span class="nv">err</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="nf">U_FAILURE</span><span class="p">(</span><span class="nv">err</span><span class="p">))</span>
<span class="k">return</span> <span class="p">(</span><span class="o">~</span><span class="p">(</span><span class="kt">PCRE2_SIZE</span><span class="p">)</span><span class="mi">0</span><span class="p">);</span>
<span class="k">return</span> <span class="nv">r</span><span class="p">;</span>
<span class="p">}</span></code></pre></div>
<p>The first and second arguments of the case callout function are the Unicode
string to transform.</p>
<p>The third and fourth arguments are the output buffer and its capacity.</p>
<p>The fifth is one of the constants <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_CASE_LOWER</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_CASE_UPPER</span></code>, or <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_CASE_TITLE_FIRST</span></code>.
<code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_CASE_LOWER</span></code> and <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_CASE_UPPER</span></code> are passed to the
callout to indicate that the case of the entire callout input should be
case-transformed. <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_CASE_TITLE_FIRST</span></code> is passed to indicate that
only the first character or glyph should be transformed to Unicode titlecase
and the rest to Unicode lowercase (note that titlecasing sometimes uses Unicode
properties to titlecase each word in a string; but PCRE2 is requesting that only
the single leading character is to be titlecased).</p>
<p>The sixth argument is the <code class="parameter pcre2-api rouge"><span class="nv">callout_data</span></code> supplied to
<code class="function pcre2-api rouge"><span class="nf">pcre2_set_substitute_case_callout()</span></code>.</p>
<p>The resulting string in the destination buffer may be larger or smaller than the
input, if the casing rules merge or split characters. The return value is the
length required for the output string. If a buffer of sufficient size was
provided to the callout, then the result must be written to the buffer and the
number of code units returned. If the result does not fit in the provided
buffer, then the required capacity must be returned and PCRE2 will not make use
of the output buffer. PCRE2 provides input and output buffers which overlap, so
the callout must support this by suitable internal buffering.</p>
<p>Alternatively, if the callout wishes to indicate an error, then it may return
<code class="c rouge" data-lang="c"><span class="p">(</span><span class="o">~</span><span class="p">(</span><span class="kt">PCRE2_SIZE</span><span class="p">)</span><span class="mi">0</span><span class="p">)</span></code>. In this case <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> will immediately fail with
error <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_REPLACECASE</span></code>.</p>
<p>When a case callout is combined with the <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_OVERFLOW_LENGTH</span></code>
option, there are situations when <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> will return an
underestimate of the required buffer size. If you call <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> once
with <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_OVERFLOW_LENGTH</span></code>, and the input buffer is too small for
the replacement string to be constructed, then instead of calling the case
callout, <code class="function pcre2-api rouge"><span class="nf">pcre2_substitute()</span></code> will make an estimate of the required buffer size.
The second call should also pass <code class="constant pcre2-api rouge"><span class="no">PCRE2_SUBSTITUTE_OVERFLOW_LENGTH</span></code>, because that
second call is not guaranteed to succeed either, if the case callout requires
more buffer space than expected. The caller must make repeated attempts in a
loop.</p></section></section>
<section class="doc-section level-1"><h2 id="_duplicate_capture_group_names">Duplicate capture group names</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_substring_nametable_scan</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="nv">stringname</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="p">*</span><span class="nv">firstptr</span><span class="p">,</span>
<span class="kt">PCRE2_SPTR</span> <span class="p">*</span><span class="nv">lastptr</span><span class="p">);</span></code></pre></div>
<p>When a pattern is compiled with the <code class="constant pcre2-api rouge"><span class="no">PCRE2_DUPNAMES</span></code> option, names for capture
groups are not required to be unique. Duplicate names are always allowed for
groups with the same number, created by using the <code class="regex rouge"><span class="pcre2-semantic">(?|</span></code> feature. Indeed, if such
groups are named, they are required to use the same names.</p>
<p>Normally, patterns that use duplicate names are such that in any one match,
only one of each set of identically-named groups participates. An example is
shown in the
<a href="./pcre2pattern.html"><code>pcre2pattern</code></a>
documentation.</p>
<p>When duplicates are present, <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_copy_byname()</span></code> and
<code class="function pcre2-api rouge"><span class="nf">pcre2_substring_get_byname()</span></code> return the first substring corresponding to
the given name that is set. Only if none are set is <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_UNSET</span></code> is
returned. The <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_number_from_name()</span></code> function returns the
error <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOUNIQUESUBSTRING</span></code> when there are duplicate names.</p>
<p>If you want to get full details of all captured substrings for a given name,
you must use the <code class="function pcre2-api rouge"><span class="nf">pcre2_substring_nametable_scan()</span></code> function. The first
argument is the compiled pattern, and the second is the name. If the third and
fourth arguments are <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, the function returns a group number for a unique
name, or <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOUNIQUESUBSTRING</span></code> otherwise.</p>
<p>When the third and fourth arguments are not <code class="constant pcre2-api rouge"><span class="kc">NULL</span></code>, they must be pointers to
variables that are updated by the function. After it has run, they point to the
first and last entries in the name-to-number table for the given name, and the
function returns the length of each entry in code units. In both cases,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOSUBSTRING</span></code> is returned if there are no entries for the given name.</p>
<p>The format of the name table is described
above
in the section <a href="#information-about-compiled-pattern">Information about a compiled pattern</a>. Given all the
relevant entries for the name, you can extract each of their numbers, and hence
the captured data.</p></section>
<section class="doc-section level-1"><h2 id="_finding_all_possible_matches_at_one_position">Finding all possible matches at one position</h2><p>The traditional matching function uses a similar algorithm to Perl, which stops
when it finds the first match at a given point in the subject. If you want to
find all possible matches, or the longest possible match at a given position,
consider using the alternative matching function (see below) instead. If you
cannot use the alternative function, you can kludge it up by making use of the
callout facility, which is described in the
<a href="./pcre2callout.html"><code>pcre2callout</code></a>
documentation.</p>
<p>What you have to do is to insert a callout right at the end of the pattern.
When your callout function is called, extract and save the current matched
substring. Then return 1, which forces <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> to backtrack and try
other alternatives. Ultimately, when it runs out of matches,
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code> will yield <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code>.</p></section>
<section class="doc-section level-1"><h2 id="_matching_a_pattern_the_alternative_function">Matching a pattern: the alternative function</h2><div class="listing-block prototype"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nf">pcre2_dfa_match</span><span class="p">(</span><span class="kt">const</span> <span class="kt">pcre2_code</span> <span class="p">*</span><span class="nv">code</span><span class="p">,</span> <span class="kt">PCRE2_SPTR</span> <span class="nv">subject</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">length</span><span class="p">,</span> <span class="kt">PCRE2_SIZE</span> <span class="nv">start_offset</span><span class="p">,</span>
<span class="kt">uint32_t</span> <span class="nv">options</span><span class="p">,</span> <span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">match_data</span><span class="p">,</span>
<span class="kt">pcre2_match_context</span> <span class="p">*</span><span class="nv">mcontext</span><span class="p">,</span> <span class="kt">int</span> <span class="p">*</span><span class="nv">workspace</span><span class="p">,</span>
<span class="kt">PCRE2_SIZE</span> <span class="nv">wscount</span><span class="p">);</span></code></pre></div>
<p>The function <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> is called to match a subject string
against a compiled pattern, using a matching algorithm that scans the subject
string just once (not counting lookaround assertions), and does not backtrack
(except when processing lookaround assertions). This has different
characteristics to the normal algorithm, and is not compatible with Perl. Some
of the features of PCRE2 patterns are not supported. Nevertheless, there are
times when this kind of matching can be useful. For a discussion of the two
matching algorithms, and a list of features that <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> does
not support, see the
<a href="./pcre2matching.html"><code>pcre2matching</code></a>
documentation.</p>
<p>The arguments for the <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> function are the same as for
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, plus two extras. The <code class="parameter pcre2-api rouge"><span class="nv">ovector</span></code> within the match data block
is used in a different way, and this is described below. The other common
arguments are used in the same way as for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, so their
description is not repeated here.</p>
<p>The two additional arguments provide workspace for the function. The workspace
vector should contain at least 20 elements. It is used for keeping track of
multiple paths through the pattern tree. More workspace is needed for patterns
and subjects where there are a lot of potential matches.</p>
<p>Here is an example of a simple call to <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>:</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="c"><span class="kt">int</span> <span class="nv">wspace</span><span class="p">[</span><span class="mi">20</span><span class="p">];</span>
<span class="kt">pcre2_match_data</span> <span class="p">*</span><span class="nv">md</span> <span class="o">=</span> <span class="nf">pcre2_match_data_create</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span> <span class="kc">NULL</span><span class="p">);</span>
<span class="kt">int</span> <span class="nv">rc</span> <span class="o">=</span> <span class="nf">pcre2_dfa_match</span><span class="p">(</span>
<span class="nv">re</span><span class="p">,</span> <span class="cm">/* result of pcre2_compile() */</span>
<span class="s">"some string"</span><span class="p">,</span> <span class="cm">/* the subject string */</span>
<span class="mi">11</span><span class="p">,</span> <span class="cm">/* the length of the subject string */</span>
<span class="mi">0</span><span class="p">,</span> <span class="cm">/* start at offset 0 in the subject */</span>
<span class="mi">0</span><span class="p">,</span> <span class="cm">/* default options */</span>
<span class="nv">md</span><span class="p">,</span> <span class="cm">/* the match data block */</span>
<span class="kc">NULL</span><span class="p">,</span> <span class="cm">/* a match context; NULL means use defaults */</span>
<span class="nv">wspace</span><span class="p">,</span> <span class="cm">/* working space vector */</span>
<span class="mi">20</span><span class="p">);</span> <span class="cm">/* number of elements (NOT size in bytes) */</span></code></pre></div>
<section class="doc-section level-2"><h3 id="_option_bits_for_pcre2_dfa_match">Option bits for <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code></h3><p>The unused bits of the <code class="parameter pcre2-api rouge"><span class="nv">options</span></code> argument for <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> must
be zero. The only bits that may be set are <code class="constant pcre2-api rouge"><span class="no">PCRE2_ANCHORED</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_COPY_MATCHED_SUBJECT</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_ENDANCHORED</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTBOL</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEOL</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEMPTY</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NOTEMPTY_ATSTART</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_UTF_CHECK</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_HARD</span></code>,
<code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_SOFT</span></code>, <code class="constant pcre2-api rouge"><span class="no">PCRE2_DFA_SHORTEST</span></code>, and <code class="constant pcre2-api rouge"><span class="no">PCRE2_DFA_RESTART</span></code>. All but the last
four of these are exactly the same as for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, so their
description is not repeated here.</p>
<dl class="options spaced" style="--tab-width: 10"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_HARD</span></code><br><code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_SOFT</span></code></span></dt><dd>These have the same general effect as they do for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, but the
details are slightly different. When <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_HARD</span></code> is set for
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>, it returns <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code> if the end of the
subject is reached and there is still at least one matching possibility that
requires additional characters. This happens even if some complete matches have
already been found. When <code class="constant pcre2-api rouge"><span class="no">PCRE2_PARTIAL_SOFT</span></code> is set, the return code
<code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOMATCH</span></code> is converted into <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_PARTIAL</span></code> if the end of the
subject is reached, there have been no complete matches, but there is still at
least one matching possibility. The portion of the string that was inspected
when the longest partial match was found is set as the first matching string in
both cases. There is a more detailed discussion of partial and multi-segment
matching, with examples, in the
<a href="./pcre2partial.html"><code>pcre2partial</code></a>
documentation.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_DFA_SHORTEST</span></code></span></dt><dd>Setting the <code class="constant pcre2-api rouge"><span class="no">PCRE2_DFA_SHORTEST</span></code> option causes the matching algorithm to stop as
soon as it has found one match. Because of the way the alternative algorithm
works, this is necessarily the shortest possible match at the first possible
matching point in the subject string.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_DFA_RESTART</span></code></span></dt><dd>When <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> returns a partial match, it is possible to call it
again, with additional subject characters, and have it continue with the same
match. The <code class="constant pcre2-api rouge"><span class="no">PCRE2_DFA_RESTART</span></code> option requests this action; when it is set, the
<code class="parameter pcre2-api rouge"><span class="nv">workspace</span></code> and <code class="parameter pcre2-api rouge"><span class="nv">wscount</span></code> options must reference the same vector as
before because data about the match so far is left in them after a partial
match. There is more discussion of this facility in the
<a href="./pcre2partial.html"><code>pcre2partial</code></a>
documentation.</dd></div></dl></section>
<section class="doc-section level-2"><h3 id="_successful_returns_from_pcre2_dfa_match">Successful returns from <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code></h3><p>When <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> succeeds, it may have matched more than one
substring in the subject. Note, however, that all the matches from one run of
the function start at the same point in the subject. The shorter matches are
all initial substrings of the longer matches. For example, if the pattern</p>
<div class="listing-block"><pre class="rouge highlight"><code data-lang="regex"><span class="pcre2-semantic">&lt;.*&gt;</span></code></pre></div>
<p>is matched against the string</p>
<div class="literal-block"><pre>This is &lt;something&gt; &lt;something else&gt; &lt;something further&gt; no more</pre></div>
<p>the three matched strings are</p>
<div class="literal-block"><pre>&lt;something&gt; &lt;something else&gt; &lt;something further&gt;
&lt;something&gt; &lt;something else&gt;
&lt;something&gt;</pre></div>
<p>On success, the yield of the function is a number greater than zero, which is
the number of matched substrings. The offsets of the substrings are returned in
the ovector, and can be extracted by number in the same way as for
<code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, but the numbers bear no relation to any capture groups
that may exist in the pattern, because DFA matching does not support capturing.</p>
<p>Calls to the convenience functions that extract substrings by name
return the error <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_DFA_UFUNC</span></code> (unsupported function) if used after a
DFA match. The convenience functions that extract substrings by number never
return <code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_NOSUBSTRING</span></code>.</p>
<p>The matched strings are stored in the ovector in reverse order of length; that
is, the longest matching string is first. If there were too many matches to fit
into the ovector, the yield of the function is zero, and the vector is filled
with the longest matches.</p>
<aside class="admonition-block note" role="note"><h6 class="block-title label-only"><span class="title-label">Note: </span></h6><p>PCRE2’s "auto-possessification" optimization usually applies to character
repeats at the end of a pattern (as well as internally). For example, the
pattern <code class="regex rouge"><span class="pcre2-semantic">a\d+</span></code> is compiled as if it were <code class="regex rouge"><span class="pcre2-semantic">a\d++</span></code>. For DFA matching, this
means that only one possible match is found. If you really do want multiple
matches in such cases, either use an ungreedy repeat such as <code class="regex rouge"><span class="pcre2-semantic">a\d+?</span></code> or set
the <code class="constant pcre2-api rouge"><span class="no">PCRE2_NO_AUTO_POSSESS</span></code> option when compiling.</p></aside></section>
<section class="doc-section level-2"><h3 id="_error_returns_from_pcre2_dfa_match">Error returns from <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code></h3><p>The <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> function returns a negative number when it fails.
Many of the errors are the same as for <code class="function pcre2-api rouge"><span class="nf">pcre2_match()</span></code>, as described
above.
There are in addition the following errors that are specific to
<code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code>:</p>
<dl class="compact" style="--tab-width: 14"><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_DFA_UITEM</span></code></span></dt><dd>This return is given if <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> encounters an item in the
pattern that it does not support, for instance, the use of <code class="regex rouge"><span class="pcre2-semantic">\C</span></code> in a UTF mode or
a backreference.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_DFA_UCOND</span></code></span></dt><dd>This return is given if <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> encounters a condition item
that uses a backreference for the condition, or a test for recursion in a
specific capture group. These are not supported.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_DFA_UINVALID_UTF</span></code></span></dt><dd>This return is given if <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> is called for a pattern that
was compiled with <code class="constant pcre2-api rouge"><span class="no">PCRE2_MATCH_INVALID_UTF</span></code>. This is not supported for DFA
matching.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_DFA_WSSIZE</span></code></span></dt><dd>This return is given if <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> runs out of space in the
<code class="parameter pcre2-api rouge"><span class="nv">workspace</span></code> vector.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_DFA_RECURSE</span></code></span></dt><dd>When a recursion or subroutine call is processed, the matching function calls
itself recursively, using private memory for the <code class="parameter pcre2-api rouge"><span class="nv">ovector</span></code> and <code class="parameter pcre2-api rouge"><span class="nv">workspace</span></code>.
This error is given if the internal <code class="parameter pcre2-api rouge"><span class="nv">ovector</span></code> is not large enough. This should be
extremely rare, as a vector of size 1,000 is used.</dd></div><div class="dlist-item"><dt><span><code class="constant pcre2-api rouge"><span class="no">PCRE2_ERROR_DFA_BADRESTART</span></code></span></dt><dd>When <code class="function pcre2-api rouge"><span class="nf">pcre2_dfa_match()</span></code> is called with the <code class="constant pcre2-api rouge"><span class="no">PCRE2_DFA_RESTART</span></code> option,
some plausibility checks are made on the contents of the workspace, which
should contain data about the previous partial match. If any of these checks
fail, this error is given.</dd></div></dl></section></section>
<section class="doc-section level-1"><h2 id="_see_also">See also</h2><p><a href="./pcre2build.html"><code>pcre2build</code></a>, <a href="./pcre2callout.html"><code>pcre2callout</code></a>, <a href="./pcre2demo.html"><code>pcre2demo</code></a>,
<a href="./pcre2matching.html"><code>pcre2matching</code></a>, <a href="./pcre2partial.html"><code>pcre2partial</code></a>, <a href="./pcre2posix.html"><code>pcre2posix</code></a>,
<a href="./pcre2sample.html"><code>pcre2sample</code></a>, <a href="./pcre2unicode.html"><code>pcre2unicode</code></a>.</p>
<h2 id="_author" class="discrete">Author</h2>
<p>Philip Hazel<br>
Retired from University Computing Service<br>
Cambridge, England.</p>
<h2 id="_revision" class="discrete">Revision</h2>
<p>Last updated: 08 December 2025<br>
Copyright © 1997-2024 University of Cambridge.</p></section></article></div></main><footer class="offline-footer"></footer></body></html>