CURLINFO_XFER_ID - Man Page

#include <curl/curl.h>

CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_XFER_ID,
                           curl_off_t *xfer_id);

Pass a pointer to a curl_off_t to receive the identifier of the current/last transfer done with the handle. Stores -1 if no transfer has been started yet for the handle.

The transfer id is unique among all transfers performed using the same connection cache. This is implicitly the case for all transfers in the same multi handle.

This functionality affects all supported protocols

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

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

    if(!res) {
      curl_off_t xfer_id;
      res = curl_easy_getinfo(curl, CURLINFO_XFER_ID, &xfer_id);
      if(!res) {
        printf("Transfer ID: %" CURL_FORMAT_CURL_OFF_T "\n", xfer_id);
      }
    }
  }
}

Added in curl 8.2.0

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

CURLINFO_CONN_ID(3), curl_easy_getinfo(3), curl_easy_setopt(3)

curl_easy_getinfo(3), CURLINFO_CONN_ID(3), CURLOPT_DEBUGFUNCTION(3).