docs/libcurl/opts/CURLOPT_DNS_CACHE_TIMEOUT.3

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.TH CURLOPT_DNS_CACHE_TIMEOUT 3 "November 04, 2020" "libcurl 7.78.0" "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, "https://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), "