## NAME

CURLMOPT_TIMERFUNCTION - set callback to receive timeout values

## SYNOPSIS

    #include <curl/curl.h>

    int timer_callback(CURLM *multi,    /* multi handle */
                       long timeout_ms, /* see above */
                       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. Each time 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 means you should delete your timer.

A timeout_ms value of 0 means you should call curl_multi_socket_action(3) or curl_multi_perform(3) (once) as soon as possible.

timer_callback will only be called when the timeout_ms changes.

The userp pointer is set with CURLMOPT_TIMERDATA.

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).

## DEFAULT

NULL

## PROTOCOLS

All

## EXAMPLE

    static gboolean timeout_cb(gpointer user_data) {
        if (user_data) {
            g_free(user_data);
            curl_multi_setopt(curl_handle, CURLMOPT_TIMERDATA, NULL);
        }
        int running;
        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, CURLMOPT_SOCKETFUNCTION

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