1
.\" $Id: curl_multi_perform.3,v 1.9 2008-12-28 21:56:56 bagder Exp $
3
.TH curl_multi_perform 3 "1 March 2002" "libcurl 7.9.5" "libcurl Manual"
5
curl_multi_perform - reads/writes available data from each easy handle
9
CURLMcode curl_multi_perform(CURLM *multi_handle, int *running_handles);
12
When the app thinks there's data available for the multi_handle, it should
13
call this function to read/write whatever there is to read or write right
14
now. curl_multi_perform() returns as soon as the reads/writes are done. This
15
function does not require that there actually is any data available for
16
reading or that data can be written, it can be called just in case. It will
17
write the number of handles that still transfer data in the second argument's
20
When you call curl_multi_perform() and the amount of \fIrunning_handles\fP is
21
changed from the previous call (or is less than the amount of easy handles
22
you've added to the multi handle), you know that there is one or more
23
transfers less "running". You can then call \fIcurl_multi_info_read(3)\fP to
24
get information about each individual completed transfer, and that returned
25
info includes CURLcode and more.
27
CURLMcode type, general libcurl multi interface error code.
29
If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this basically means that you
30
should call \fIcurl_multi_perform\fP again, before you select() on more
31
actions. You don't have to do it immediately, but the return code means that
32
libcurl may have more data available to return or that there may be more data
33
to send off before it is "satisfied". Do note that \fIcurl_multi_perform(3)\fP
34
will return \fICURLM_CALL_MULTI_PERFORM\fP only when it wants to be called
35
again \fBimmediately\fP. When things are fine and there is nothing immediate
36
it wants done, it'll return \fICURLM_OK\fP and you need to wait for \&"action"
37
and then call this function again.
39
NOTE that this only returns errors etc regarding the whole multi stack. Problems
40
still might have occurred on individual transfers even when this
41
function returns \fICURLM_OK\fP.
43
Most applications will use \fIcurl_multi_fdset(3)\fP to get the multi_handle's
44
file descriptors, then it'll wait for action on them using \fBselect(3)\fP and
45
as soon as one or more of them are ready, \fIcurl_multi_perform(3)\fP gets
48
.BR curl_multi_cleanup "(3), " curl_multi_init "(3), "
49
.BR curl_multi_fdset "(3), " curl_multi_info_read "(3), "
50
.BR libcurl-errors "(3)"