.\" **************************************************************************
.\" *                                  _   _ ____  _
.\" *  Project                     ___| | | |  _ \| |
.\" *                             / __| | | | |_) | |
.\" *                            | (__| |_| |  _ <| |___
.\" *                             \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
.\" * are also available at https://curl.haxx.se/docs/copyright.html.
.\" *
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
.\" * copies of the Software, and permit persons to whom the Software is
.\" * furnished to do so, under the terms of the COPYING file.
.\" *
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
.\" * KIND, either express or implied.
.\" *
.\" **************************************************************************
.\"
.TH CURLOPT_DNS_CACHE_TIMEOUT 3 "17 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
.SH NAME
CURLOPT_DNS_CACHE_TIMEOUT \- set life-time for DNS cache entries
.SH SYNOPSIS
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_CACHE_TIMEOUT, long age);
.SH DESCRIPTION
Pass a long, this sets the timeout in seconds. Name resolves will be kept in
memory and used for this number of seconds. Set to zero to completely disable
caching, or set to -1 to make the cached entries remain forever. By default,
libcurl caches this info for 60 seconds.

The name resolve functions of various libc implementations don't re-read name
server information unless explicitly told so (for example, by calling
\fIres_init(3)\fP). This may cause libcurl to keep using the older server even
if DHCP has updated the server info, and this may look like a DNS cache issue
to the casual libcurl-app user.

Note that DNS entries have a "TTL" property but libcurl doesn't use that. This
DNS cache timeout is entirely speculative that a name will resolve to the same
address for a certain small amount of time into the future.
.SH DEFAULT
60
.SH PROTOCOLS
All
.SH EXAMPLE
.nf
CURL *curl = curl_easy_init();
if(curl) {
  curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/foo.bin");

  /* only reuse addresses for a very short time */
  curl_easy_setopt(curl, CURLOPT_DNS_CACHE_TIMEOUT, 2L);

  ret = curl_easy_perform(curl);

  /* in this second request, the cache will not be used if more than
     two seconds have passed since the previous name resolve */
  ret = curl_easy_perform(curl);

  curl_easy_cleanup(curl);
}
.fi
.SH AVAILABILITY
Always
.SH RETURN VALUE
Returns CURLE_OK
.SH "SEE ALSO"
.BR CURLOPT_DNS_USE_GLOBAL_CACHE "(3), " CURLOPT_DNS_SERVERS "(3), "
.BR CURLOPT_RESOLVE "(3), "