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23 .TH CURLOPT_DNS_CACHE_TIMEOUT 3 "December 09, 2017" "libcurl 7.59.0" "curl_easy_setopt options"
26 CURLOPT_DNS_CACHE_TIMEOUT \- set life-time for DNS cache entries
28 #include <curl/curl.h>
30 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_CACHE_TIMEOUT, long age);
32 Pass a long, this sets the timeout in seconds. Name resolves will be kept in
33 memory and used for this number of seconds. Set to zero to completely disable
34 caching, or set to -1 to make the cached entries remain forever. By default,
35 libcurl caches this info for 60 seconds.
37 The name resolve functions of various libc implementations don't re-read name
38 server information unless explicitly told so (for example, by calling
39 \fIres_init(3)\fP). This may cause libcurl to keep using the older server even
40 if DHCP has updated the server info, and this may look like a DNS cache issue
41 to the casual libcurl-app user.
43 Note that DNS entries have a "TTL" property but libcurl doesn't use that. This
44 DNS cache timeout is entirely speculative that a name will resolve to the same
45 address for a certain small amount of time into the future.
52 CURL *curl = curl_easy_init();
54 curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/foo.bin");
56 /* only reuse addresses for a very short time */
57 curl_easy_setopt(curl, CURLOPT_DNS_CACHE_TIMEOUT, 2L);
59 ret = curl_easy_perform(curl);
61 /* in this second request, the cache will not be used if more than
62 two seconds have passed since the previous name resolve */
63 ret = curl_easy_perform(curl);
65 curl_easy_cleanup(curl);
73 .BR CURLOPT_DNS_USE_GLOBAL_CACHE "(3), " CURLOPT_DNS_SERVERS "(3), "
74 .BR CURLOPT_RESOLVE "(3), "