curl_multi_wait(3)

curl_multi_wait(3)       libcurl Manual        curl_multi_wait(3)

NAME

     curl_multi_wait - polls on all easy handles in a multi  han-
     dle

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 interest-
     ing 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.

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curl_multi_wait(3)       libcurl Manual        curl_multi_wait(3)

     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);

libcurl 7.58.0     Last change: March 09, 2016                  2

curl_multi_wait(3)       libcurl Manual        curl_multi_wait(3)

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)

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