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curl/docs/libcurl/opts/CURLOPT_DNS_CACHE_TIMEOUT.3

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+.TH CURLOPT_DNS_CACHE_TIMEOUT 3 "November 04, 2020" "libcurl 7.75.0" "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), "