curl_multi_info_read(3)         libcurl Manual         curl_multi_info_read(3)

NAME
       curl_multi_info_read - read multi stack informationals

SYNOPSIS
       #include <curl/curl.h>

       CURLMsg *curl_multi_info_read( CURLM *multi_handle,
                                      int *msgs_in_queue);

DESCRIPTION
       Ask  the multi handle if there are any messages/informationals from the
       individual transfers. Messages may include informationals  such  as  an
       error  code  from the transfer or just the fact that a transfer is com-
       pleted. More details on these should be written down as well.

       Repeated calls to this function will return a  new  struct  each  time,
       until  a  NULL  is returned as a signal that there is no more to get at
       this point. The integer pointed to with msgs_in_queue will contain  the
       number of remaining messages after this function was called.

       When  you  fetch  a message using this function, it is removed from the
       internal queue so calling this function again will not return the  same
       message  again.  It will instead return new messages at each new invoke
       until the queue is emptied.

       WARNING: The data the returned pointer points to will not survive call-
       ing      curl_multi_cleanup(3),      curl_multi_remove_handle(3)     or
       curl_easy_cleanup(3).

       The 'CURLMsg' struct is very simple and only contains very basic infor-
       mation.   If  more involved information is wanted, the particular "easy
       handle" is present in that struct and can be used in subsequent regular
       curl_easy_getinfo(3) calls (or similar):

        struct CURLMsg {
          CURLMSG msg;       /* what this message means */
          CURL *easy_handle; /* the handle it concerns */
          union {
            void *whatever;    /* message-specific data */
            CURLcode result;   /* return code for transfer */
          } data;
        };
       When  msg  is  CURLMSG_DONE,  the message identifies a transfer that is
       done, and then result contains the return code for the easy handle that
       just completed.

       At this point, there are no other msg types defined.

EXAMPLE
       struct CURLMsg *m;

       /* call curl_multi_perform or curl_multi_socket_action first, then loop
          through and check if there are any transfers that have completed */

       do {
         int msgq = 0;
         m = curl_multi_info_read(multi_handle, &msgq);
         if(m && (m->msg == CURLMSG_DONE)) {
           CURL *e = m->easy_handle;
           transfers--;
           curl_multi_remove_handle(multi_handle, e);
           curl_easy_cleanup(e);
         }
       } while(m);

RETURN VALUE
       A  pointer  to  a  filled-in struct, or NULL if it failed or ran out of
       structs. It also writes the number of messages left in the queue (after
       this read) in the integer the second argument points to.

SEE ALSO
       curl_multi_cleanup(3), curl_multi_init(3), curl_multi_perform(3)

libcurl 7.54.0                 February 03, 2016       curl_multi_info_read(3)