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CURLMOPT_TIMERFUNCTION(3)           libcurl          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 *clientp);    /* 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 expire time of timeout_ms milliseconds. 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 clientp pointer is set with CURLMOPT_TIMERDATA(3).

       The timer callback should return 0 on success, and -1 on error. If this
       callback returns error, all transfers currently in progress in this
       multi handle will be aborted and fail.

       This callback can be used instead of, or in addition to,
       curl_multi_timeout(3).

       WARNING: do not call 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 *clientp)
       {
         guint *id = clientp;

         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);
         }
         current_timer = 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),

ibcurl 8.1.2                    April 26, 2023       CURLMOPT_TIMERFUNCTION(3)