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, un-
til 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 num-
ber 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 simple and only contains basic information. 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);
AVAILABILITY
Added in 7.9.6
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 7.81.0 November 26, 2021 curl_multi_info_read(3)
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