NAME

       curl_multi_wait - polls on all easy handles in a multi handle

SYNOPSIS

       #include <curl/curl.h>

       CURLMcode curl_multi_wait(CURLM *multi_handle,
                                 struct curl_waitfd extra_fds[],
                                 unsigned int extra_nfds,
                                 int timeout_ms,
                                 int *numfds);

DESCRIPTION

       curl_multi_wait(3)  polls  all file descriptors used by the curl easy handles contained in
       the given multi handle set.  It will block until activity is detected on at least  one  of
       the  handles  or  timeout_ms has passed.  Alternatively, if the multi handle has a pending
       internal timeout that has a shorter expiry time than timeout_ms, that shorter time will be
       used instead to make sure timeout accuracy is reasonably kept.

       The  calling  application  may pass additional curl_waitfd structures which are similar to
       poll(2)'s pollfd structure to be waited on in the same call.

       On completion, if numfds is non-NULL, it will be populated with the total number  of  file
       descriptors  on  which  interesting  events occurred. This number can include both libcurl
       internal descriptors as well as descriptors provided in extra_fds.

       If no extra file descriptors are provided and libcurl has no file descriptor to  offer  to
       wait for, this function will return immediately.

       This function is encouraged to be used instead of select(3) when using the multi interface
       to allow applications to easier circumvent the  common  problem  with  1024  maximum  file
       descriptors.

curl_waitfd

       struct curl_waitfd {
         curl_socket_t fd;
         short events;
         short revents;
       };

       CURL_WAIT_POLLIN
              Bit  flag  to  curl_waitfd.events  indicating the socket should poll on read events
              such as new data received.

       CURL_WAIT_POLLPRI
              Bit flag to curl_waitfd.events indicating the socket should poll on  high  priority
              read events such as out of band data.

       CURL_WAIT_POLLOUT
              Bit  flag  to  curl_waitfd.events indicating the socket should poll on write events
              such as the socket being clear to write without blocking.

EXAMPLE

       CURL *easy_handle;
       CURLM *multi_handle;

       /* add the individual easy handle */
       curl_multi_add_handle(multi_handle, easy_handle);

       do {
         CURLMcode mc;
         int numfds;

         mc = curl_multi_perform(multi_handle, &still_running);

         if(mc == CURLM_OK ) {
           /* wait for activity, timeout or "nothing" */
           mc = curl_multi_wait(multi_handle, NULL, 0, 1000, &numfds);
         }

         if(mc != CURLM_OK) {
           fprintf(stderr, "curl_multi failed, code %d.0, mc);
           break;
         }

         /* 'numfds' being zero means either a timeout or no file descriptors to
            wait for. Try timeout on first occurrence, then assume no file
            descriptors and no file descriptors to wait for means wait for 100
            milliseconds. */

         if(!numfds) {
           repeats++; /* count number of repeated zero numfds */
           if(repeats > 1) {
             WAITMS(100); /* sleep 100 milliseconds */
           }
         }
         else
           repeats = 0;

       } while(still_running);

       curl_multi_remove_handle(multi_handle, easy_handle);

RETURN VALUE

       CURLMcode type, general libcurl multi interface error code. See libcurl-errors(3)

AVAILABILITY

       This function was added in libcurl 7.28.0.

SEE ALSO

       curl_multi_fdset(3), curl_multi_perform(3)