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| .TH CURLOPT_DNS_CACHE_TIMEOUT 3 "17 Jun 2014" libcurl libcurl |
| .SH NAME |
| CURLOPT_DNS_CACHE_TIMEOUT \- life-time for DNS cache entries |
| .SH SYNOPSIS |
| .nf |
| #include <curl/curl.h> |
| |
| CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_CACHE_TIMEOUT, long age); |
| .fi |
| .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. |
| |
| We recommend users not to tamper with this option unless strictly necessary. |
| If you do, be careful of using large values that can make the cache size grow |
| significantly if many different host names are used within that timeout |
| period. |
| |
| The name resolve functions of various libc implementations do not 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. |
| |
| DNS entries have a "TTL" property but libcurl does not 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. |
| |
| Since version 8.1.0, libcurl prunes entries from the DNS cache if it exceeds |
| 30,000 entries no matter which timeout value is used. |
| .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 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), " |
