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CURLMOPT_TIMERFUNCTION(3)  curl_multi_setopt options CURLMOPT_TIMERFUNCTION(3)

NAME
       CURLMOPT_TIMERFUNCTION - callback to receive timeout values

SYNOPSIS
       #include <curl/curl.h>

       int timer_callback(CURLM *multi,    /* multi handle */
                          long timeout_ms, /* timeout in number of ms */
                          void *userp);    /* private callback pointer */

       CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_TIMERFUNCTION, timer_callback);

DESCRIPTION
       Pass a pointer to your callback function, which should match the
       prototype shown above.

       Certain features, such as timeouts and retries, require you to call
       libcurl even when there is no activity on the file descriptors.

       Your callback function timer_callback should install a non-repeating
       timer with an interval of timeout_ms. When that timer fires, call
       either curl_multi_socket_action(3) or curl_multi_perform(3), depending
       on which interface you use.

       A timeout_ms value of -1 passed to this callback means you should
       delete the timer. All other values are valid expire times in number of
       milliseconds.

       The timer_callback will only be called when the timeout expire time is
       changed.

       The userp pointer is set with CURLMOPT_TIMERDATA(3).

       The timer callback should return 0 on success, and -1 on error. This
       callback can be used instead of, or in addition to,
       curl_multi_timeout(3).

       WARNING: even if it feels tempting, avoid calling libcurl directly from
       within the callback itself when the timeout_ms value is zero, since it
       risks triggering an unpleasant recursive behavior that immediately
       calls another call to the callback with a zero timeout...

DEFAULT
       NULL

PROTOCOLS
       All

EXAMPLE
       static gboolean timeout_cb(gpointer user_data)
       {
         int running;
         if(user_data) {
           g_free(user_data);
           curl_multi_setopt(curl_handle, CURLMOPT_TIMERDATA, NULL);
         }
         curl_multi_socket_action(multi, CURL_SOCKET_TIMEOUT, 0, &running);
         return G_SOURCE_REMOVE;
       }

       static int timerfunc(CURLM *multi, long timeout_ms, void *userp)
       {
         guint *id = userp;

         if(id)
           g_source_remove(*id);

         /* -1 means we should just delete our timer. */
         if(timeout_ms == -1) {
           g_free(id);
           id = NULL;
         }
         else {
           if(!id)
             id = g_new(guint, 1);
           *id = g_timeout_add(timeout_ms, timeout_cb, id);
         }
         curl_multi_setopt(multi, CURLMOPT_TIMERDATA, id);
         return 0;
       }

       curl_multi_setopt(multi, CURLMOPT_TIMERFUNCTION, timerfunc);

AVAILABILITY
       Added in 7.16.0

RETURN VALUE
       Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION
       if not.

SEE ALSO
       CURLMOPT_TIMERDATA(3), CURLMOPT_SOCKETFUNCTION(3),

libcurl 7.79.1                 September 8, 2021     CURLMOPT_TIMERFUNCTION(3)