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* Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
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CURLINFO_CONDITION_UNMET - get info on unmet time conditional or 304 HTTP response. #include <curl/curl.h> CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_CONDITION_UNMET, long *unmet); Pass a pointer to a long to receive the number 1 if the condition provided in the previous request did not match (see CURLOPT_TIMECONDITION(3)). Alas, if this returns a 1 you know that the reason you did not get data in return is because it did not fulfill the condition. The long this argument points to will get a zero stored if the condition instead was met. This can also return 1 if the server responded with a 304 HTTP status code, for example after sending a custom "If-Match-*" header. HTTP and some

CURL *curl = curl_easy_init();
if(curl) {
 curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

 /* January 1, 2020 is 1577833200 */
 curl_easy_setopt(curl, CURLOPT_TIMEVALUE, 1577833200L);

 /* If-Modified-Since the above time stamp */
 curl_easy_setopt(curl, CURLOPT_TIMECONDITION, CURL_TIMECOND_IFMODSINCE);

 /* Perform the request */
 res = curl_easy_perform(curl);

 if(!res) {
 /* check the time condition */
 long unmet;
 res = curl_easy_getinfo(curl, CURLINFO_CONDITION_UNMET, &unmet);
 if(!res) {
 printf("The time condition was %sfulfilled\\n", unmet?"NOT":"");
 }
 }
}

Added in 7.19.4 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not. curl_easy_getinfo "(3), " curl_easy_setopt "(3), "