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| </style><title>FAQ</title></head><body bgcolor="#8b7765" text="#000000" link="#a06060" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"><a href="http://swpat.ffii.org/"><img src="epatents.png" alt="Action against software patents" /></a></td><td width="180"><a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo" /></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo" /></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo" /></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo" /></a></div></td><td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center"><h1>The XML C parser and toolkit of Gnome</h1><h2>FAQ</h2></td></tr></table></td></tr></table></td></tr></table><table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html">Home</a></li><li><a href="html/index.html">Reference Manual</a></li><li><a href="intro.html">Introduction</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="docs.html" style="font-weight:bold">Developer Menu</a></li><li><a href="bugs.html">Reporting bugs and getting help</a></li><li><a href="help.html">How to help</a></li><li><a href="downloads.html">Downloads</a></li><li><a href="news.html">Releases</a></li><li><a href="XMLinfo.html">XML</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="xmldtd.html">Validation & DTDs</a></li><li><a href="encoding.html">Encodings support</a></li><li><a href="catalog.html">Catalog support</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="contribs.html">Contributions</a></li><li><a href="examples/index.html" style="font-weight:bold">Code Examples</a></li><li><a href="html/index.html" style="font-weight:bold">API Menu</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="ChangeLog.html">Recent Changes</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><a href="ftp://xmlsoft.org/">FTP</a></li><li><a href="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><a href="http://opencsw.org/packages/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://lxml.de/">lxml Python bindings</a></li><li><a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl bindings</a></li><li><a href="http://libxmlplusplus.sourceforge.net/">C++ bindings</a></li><li><a href="http://www.zend.com/php5/articles/php5-xmlphp.php#Heading4">PHP bindings</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://libxml.rubyforge.org/">Ruby bindings</a></li><li><a href="http://tclxml.sourceforge.net/">Tcl bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd"><p>Table of Contents:</p><ul> |
| <li><a href="FAQ.html#License">License(s)</a></li> |
| <li><a href="FAQ.html#Installati">Installation</a></li> |
| <li><a href="FAQ.html#Compilatio">Compilation</a></li> |
| <li><a href="FAQ.html#Developer">Developer corner</a></li> |
| </ul><h3><a name="License" id="License">License</a>(s)</h3><ol> |
| <li><em>Licensing Terms for libxml</em> |
| <p>libxml2 is released under the <a href="http://www.opensource.org/licenses/mit-license.html">MIT |
| License</a>; see the file Copyright in the distribution for the precise |
| wording</p> |
| </li> |
| <li><em>Can I embed libxml2 in a proprietary application ?</em> |
| <p>Yes. The MIT License allows you to keep proprietary the changes you |
| made to libxml, but it would be graceful to send-back bug fixes and |
| improvements as patches for possible incorporation in the main |
| development tree.</p> |
| </li> |
| </ol><h3><a name="Installati" id="Installati">Installation</a></h3><ol> |
| <li><strong><span style="background-color: #FF0000">Do Not Use |
| libxml1</span></strong>, use libxml2</li> |
| <p></p> |
| <li><em>Where can I get libxml</em> ? |
| <p>The original distribution comes from <a href="ftp://xmlsoft.org/libxml2/">xmlsoft.org</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.6/">gnome.org</a></p> |
| <p>Most Linux and BSD distributions include libxml, this is probably the |
| safer way for end-users to use libxml.</p> |
| <p>David Doolin provides precompiled Windows versions at <a href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/ ">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p> |
| </li> |
| <p></p> |
| <li><em>I see libxml and libxml2 releases, which one should I install ?</em> |
| <ul> |
| <li>If you are not constrained by backward compatibility issues with |
| existing applications, install libxml2 only</li> |
| <li>If you are not doing development, you can safely install both. |
| Usually the packages <a href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a> are |
| compatible (this is not the case for development packages).</li> |
| <li>If you are a developer and your system provides separate packaging |
| for shared libraries and the development components, it is possible |
| to install libxml and libxml2, and also <a href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a> |
| and <a href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a> |
| too for libxml2 >= 2.3.0</li> |
| <li>If you are developing a new application, please develop against |
| libxml2(-devel)</li> |
| </ul> |
| </li> |
| <li><em>I can't install the libxml package, it conflicts with libxml0</em> |
| <p>You probably have an old libxml0 package used to provide the shared |
| library for libxml.so.0, you can probably safely remove it. The libxml |
| packages provided on <a href="ftp://xmlsoft.org/libxml2/">xmlsoft.org</a> provide |
| libxml.so.0</p> |
| </li> |
| <li><em>I can't install the libxml(2) RPM package due to failed |
| dependencies</em> |
| <p>The most generic solution is to re-fetch the latest src.rpm , and |
| rebuild it locally with</p> |
| <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p> |
| <p>If everything goes well it will generate two binary rpm packages (one |
| providing the shared libs and xmllint, and the other one, the -devel |
| package, providing includes, static libraries and scripts needed to build |
| applications with libxml(2)) that you can install locally.</p> |
| </li> |
| </ol><h3><a name="Compilatio" id="Compilatio">Compilation</a></h3><ol> |
| <li><em>What is the process to compile libxml2 ?</em> |
| <p>As most UNIX libraries libxml2 follows the "standard":</p> |
| <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p> |
| <p><code>cd libxml-xxxx</code></p> |
| <p><code>./configure --help</code></p> |
| <p>to see the options, then the compilation/installation proper</p> |
| <p><code>./configure [possible options]</code></p> |
| <p><code>make</code></p> |
| <p><code>make install</code></p> |
| <p>At that point you may have to rerun ldconfig or a similar utility to |
| update your list of installed shared libs.</p> |
| </li> |
| <li><em>What other libraries are needed to compile/install libxml2 ?</em> |
| <p>Libxml2 does not require any other library, the normal C ANSI API |
| should be sufficient (please report any violation to this rule you may |
| find).</p> |
| <p>However if found at configuration time libxml2 will detect and use the |
| following libs:</p> |
| <ul> |
| <li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a |
| highly portable and available widely compression library.</li> |
| <li>iconv: a powerful character encoding conversion library. It is |
| included by default in recent glibc libraries, so it doesn't need to |
| be installed specifically on Linux. It now seems a <a href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part |
| of the official UNIX</a> specification. Here is one <a href="http://www.gnu.org/software/libiconv/">implementation of the |
| library</a> which source can be found <a href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li> |
| </ul> |
| </li> |
| <p></p> |
| <li><em>Make check fails on some platforms</em> |
| <p>Sometimes the regression tests' results don't completely match the |
| value produced by the parser, and the makefile uses diff to print the |
| delta. On some platforms the diff return breaks the compilation process; |
| if the diff is small this is probably not a serious problem.</p> |
| <p>Sometimes (especially on Solaris) make checks fail due to limitations |
| in make. Try using GNU-make instead.</p> |
| </li> |
| <li><em>I use the SVN version and there is no configure script</em> |
| <p>The configure script (and other Makefiles) are generated. Use the |
| autogen.sh script to regenerate the configure script and Makefiles, |
| like:</p> |
| <p><code>./autogen.sh --prefix=/usr --disable-shared</code></p> |
| </li> |
| <li><em>I have troubles when running make tests with gcc-3.0</em> |
| <p>It seems the initial release of gcc-3.0 has a problem with the |
| optimizer which miscompiles the URI module. Please use another |
| compiler.</p> |
| </li> |
| </ol><h3><a name="Developer" id="Developer">Developer</a> corner</h3><ol> |
| <li><em>Troubles compiling or linking programs using libxml2</em> |
| <p>Usually the problem comes from the fact that the compiler doesn't get |
| the right compilation or linking flags. There is a small shell script |
| <code>xml2-config</code> which is installed as part of libxml2 usual |
| install process which provides those flags. Use</p> |
| <p><code>xml2-config --cflags</code></p> |
| <p>to get the compilation flags and</p> |
| <p><code>xml2-config --libs</code></p> |
| <p>to get the linker flags. Usually this is done directly from the |
| Makefile as:</p> |
| <p><code>CFLAGS=`xml2-config --cflags`</code></p> |
| <p><code>LIBS=`xml2-config --libs`</code></p> |
| </li> |
| <li><em>I want to install my own copy of libxml2 in my home directory and |
| link my programs against it, but it doesn't work</em> |
| <p>There are many different ways to accomplish this. Here is one way to |
| do this under Linux. Suppose your home directory is <code>/home/user. |
| </code>Then:</p> |
| <ul> |
| <li>Create a subdirectory, let's call it <code>myxml</code></li> |
| <li>unpack the libxml2 distribution into that subdirectory</li> |
| <li>chdir into the unpacked distribution |
| (<code>/home/user/myxml/libxml2 </code>)</li> |
| <li>configure the library using the "<code>--prefix</code>" switch, |
| specifying an installation subdirectory in |
| <code>/home/user/myxml</code>, e.g. |
| <p><code>./configure --prefix /home/user/myxml/xmlinst</code> {other |
| configuration options}</p> |
| </li> |
| <li>now run <code>make</code> followed by <code>make install</code></li> |
| <li>At this point, the installation subdirectory contains the complete |
| "private" include files, library files and binary program files (e.g. |
| xmllint), located in |
| <p><code>/home/user/myxml/xmlinst/lib, |
| /home/user/myxml/xmlinst/include </code> and <code> |
| /home/user/myxml/xmlinst/bin</code></p> |
| respectively.</li> |
| <li>In order to use this "private" library, you should first add it to |
| the beginning of your default PATH (so that your own private program |
| files such as xmllint will be used instead of the normal system |
| ones). To do this, the Bash command would be |
| <p><code>export PATH=/home/user/myxml/xmlinst/bin:$PATH</code></p> |
| </li> |
| <li>Now suppose you have a program <code>test1.c</code> that you would |
| like to compile with your "private" library. Simply compile it using |
| the command |
| <p><code>gcc `xml2-config --cflags --libs` -o test test.c</code></p> |
| Note that, because your PATH has been set with <code> |
| /home/user/myxml/xmlinst/bin</code> at the beginning, the xml2-config |
| program which you just installed will be used instead of the system |
| default one, and this will <em>automatically</em> get the correct |
| libraries linked with your program.</li> |
| </ul> |
| </li> |
| |
| <p></p> |
| <li><em>xmlDocDump() generates output on one line.</em> |
| <p>Libxml2 will not <strong>invent</strong> spaces in the content of a |
| document since <strong>all spaces in the content of a document are |
| significant</strong>. If you build a tree from the API and want |
| indentation:</p> |
| <ol> |
| <li>the correct way is to generate those yourself too.</li> |
| <li>the dangerous way is to ask libxml2 to add those blanks to your |
| content <strong>modifying the content of your document in the |
| process</strong>. The result may not be what you expect. There is |
| <strong>NO</strong> way to guarantee that such a modification won't |
| affect other parts of the content of your document. See <a href="http://xmlsoft.org/html/libxml-parser.html#xmlKeepBlanksDefault">xmlKeepBlanksDefault |
| ()</a> and <a href="http://xmlsoft.org/html/libxml-tree.html#xmlSaveFormatFile">xmlSaveFormatFile |
| ()</a></li> |
| </ol> |
| </li> |
| <p></p> |
| <li><em>Extra nodes in the document:</em> |
| <p><em>For an XML file as below:</em></p> |
| <pre><?xml version="1.0"?> |
| <PLAN xmlns="http://www.argus.ca/autotest/1.0/"> |
| <NODE CommFlag="0"/> |
| <NODE CommFlag="1"/> |
| </PLAN></pre> |
| <p><em>after parsing it with the function |
| pxmlDoc=xmlParseFile(...);</em></p> |
| <p><em>I want to the get the content of the first node (node with the |
| CommFlag="0")</em></p> |
| <p><em>so I did it as following;</em></p> |
| <pre>xmlNodePtr pnode; |
| pnode=pxmlDoc->children->children;</pre> |
| <p><em>but it does not work. If I change it to</em></p> |
| <pre>pnode=pxmlDoc->children->children->next;</pre> |
| <p><em>then it works. Can someone explain it to me.</em></p> |
| <p></p> |
| <p>In XML all characters in the content of the document are significant |
| <strong>including blanks and formatting line breaks</strong>.</p> |
| <p>The extra nodes you are wondering about are just that, text nodes with |
| the formatting spaces which are part of the document but that people tend |
| to forget. There is a function <a href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault |
| ()</a> to remove those at parse time, but that's an heuristic, and its |
| use should be limited to cases where you are certain there is no |
| mixed-content in the document.</p> |
| </li> |
| <li><em>I get compilation errors of existing code like when accessing |
| <strong>root</strong> or <strong>child fields</strong> of nodes.</em> |
| <p>You are compiling code developed for libxml version 1 and using a |
| libxml2 development environment. Either switch back to libxml v1 devel or |
| even better fix the code to compile with libxml2 (or both) by <a href="upgrade.html">following the instructions</a>.</p> |
| </li> |
| <li><em>I get compilation errors about non existing |
| <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong> |
| fields.</em> |
| <p>The source code you are using has been <a href="upgrade.html">upgraded</a> to be able to compile with both libxml |
| and libxml2, but you need to install a more recent version: |
| libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p> |
| </li> |
| <li><em>Random crashes in threaded applications</em> |
| <p>Read and follow all advices on the <a href="threads.html">thread |
| safety</a> page, and make 100% sure you never call xmlCleanupParser() |
| while the library or an XML document might still be in use by another |
| thread.</p> |
| </li> |
| <li><em>The example provided in the web page does not compile.</em> |
| <p>It's hard to maintain the documentation in sync with the code |
| <grin/> ...</p> |
| <p>Check the previous points 1/ and 2/ raised before, and please send |
| patches.</p> |
| </li> |
| <li><em>Where can I get more examples and information than provided on the |
| web page?</em> |
| <p>Ideally a libxml2 book would be nice. I have no such plan ... But you |
| can:</p> |
| <ul> |
| <li>check more deeply the <a href="html/libxml-lib.html">existing |
| generated doc</a></li> |
| <li>have a look at <a href="examples/index.html">the set of |
| examples</a>.</li> |
| <li>look for examples of use for libxml2 function using the Gnome code |
| or by asking on Google.</li> |
| <li><a href="http://svn.gnome.org/viewvc/libxml2/trunk/">Browse |
| the libxml2 source</a> , I try to write code as clean and documented |
| as possible, so looking at it may be helpful. In particular the code |
| of <a href="http://svn.gnome.org/viewvc/libxml2/trunk/xmllint.c?view=markup">xmllint.c</a> and of the various testXXX.c test programs should |
| provide good examples of how to do things with the library.</li> |
| </ul> |
| </li> |
| <p></p> |
| <li><em>What about C++ ?</em> |
| <p>libxml2 is written in pure C in order to allow easy reuse on a number |
| of platforms, including embedded systems. I don't intend to convert to |
| C++.</p> |
| <p>There is however a C++ wrapper which may fulfill your needs:</p> |
| <ul> |
| <li>by Ari Johnson <ari@btigate.com>: |
| <p>Website: <a href="http://libxmlplusplus.sourceforge.net/">http://libxmlplusplus.sourceforge.net/</a></p> |
| <p>Download: <a href="http://sourceforge.net/project/showfiles.php?group_id=12999">http://sourceforge.net/project/showfiles.php?group_id=12999</a></p> |
| </li> |
| </ul> |
| </li> |
| <li><em>How to validate a document a posteriori ?</em> |
| <p>It is possible to validate documents which had not been validated at |
| initial parsing time or documents which have been built from scratch |
| using the API. Use the <a href="http://xmlsoft.org/html/libxml-valid.html#xmlValidateDtd">xmlValidateDtd()</a> |
| function. It is also possible to simply add a DTD to an existing |
| document:</p> |
| <pre>xmlDocPtr doc; /* your existing document */ |
| xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ |
| |
| dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ |
| |
| doc->intSubset = dtd; |
| if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); |
| else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); |
| </pre> |
| </li> |
| <li><em>So what is this funky "xmlChar" used all the time?</em> |
| <p>It is a null terminated sequence of utf-8 characters. And only utf-8! |
| You need to convert strings encoded in different ways to utf-8 before |
| passing them to the API. This can be accomplished with the iconv library |
| for instance.</p> |
| </li> |
| <li>etc ...</li> |
| </ol><p></p><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html> |
