1curl_multi_info_read(3)         libcurl Manual         curl_multi_info_read(3)
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NAME

6       curl_multi_info_read - read multi stack informationals
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SYNOPSIS

9       #include <curl/curl.h>
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11       CURLMsg *curl_multi_info_read( CURLM *multi_handle,
12                                      int *msgs_in_queue);
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DESCRIPTION

15       Ask  the multi handle if there are any messages/informationals from the
16       individual transfers. Messages may include informationals  such  as  an
17       error  code  from the transfer or just the fact that a transfer is com‐
18       pleted. More details on these should be written down as well.
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20       Repeated calls to this function will return a new struct each time, un‐
21       til a NULL is returned as a signal that there is no more to get at this
22       point. The integer pointed to with msgs_in_queue will contain the  num‐
23       ber of remaining messages after this function was called.
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25       When  you  fetch  a message using this function, it is removed from the
26       internal queue so calling this function again will not return the  same
27       message  again.  It will instead return new messages at each new invoke
28       until the queue is emptied.
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30       WARNING: The data the returned pointer points to will not survive call‐
31       ing      curl_multi_cleanup(3),      curl_multi_remove_handle(3)     or
32       curl_easy_cleanup(3).
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34       The 'CURLMsg' struct is very simple and only contains very basic infor‐
35       mation.   If  more involved information is wanted, the particular "easy
36       handle" is present in that struct and can be used in subsequent regular
37       curl_easy_getinfo(3) calls (or similar):
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39        struct CURLMsg {
40          CURLMSG msg;       /* what this message means */
41          CURL *easy_handle; /* the handle it concerns */
42          union {
43            void *whatever;    /* message-specific data */
44            CURLcode result;   /* return code for transfer */
45          } data;
46        };
47       When  msg  is  CURLMSG_DONE,  the message identifies a transfer that is
48       done, and then result contains the return code for the easy handle that
49       just completed.
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51       At this point, there are no other msg types defined.
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EXAMPLE

54       struct CURLMsg *m;
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56       /* call curl_multi_perform or curl_multi_socket_action first, then loop
57          through and check if there are any transfers that have completed */
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59       do {
60         int msgq = 0;
61         m = curl_multi_info_read(multi_handle, &msgq);
62         if(m && (m->msg == CURLMSG_DONE)) {
63           CURL *e = m->easy_handle;
64           transfers--;
65           curl_multi_remove_handle(multi_handle, e);
66           curl_easy_cleanup(e);
67         }
68       } while(m);
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RETURN VALUE

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

76       curl_multi_cleanup(3), curl_multi_init(3), curl_multi_perform(3)
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80libcurl 7.76.1                 November 04, 2020       curl_multi_info_read(3)
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