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51 lines
2.4 KiB
Groff
51 lines
2.4 KiB
Groff
.\" $Id$
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.\"
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.TH curl_multi_perform 3 "1 March 2002" "libcurl 7.9.5" "libcurl Manual"
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.SH NAME
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curl_multi_perform - reads/writes available data from each easy handle
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.SH SYNOPSIS
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#include <curl/curl.h>
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CURLMcode curl_multi_perform(CURLM *multi_handle, int *running_handles);
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.ad
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.SH DESCRIPTION
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When the app thinks there's data available for the multi_handle, it should
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call this function to read/write whatever there is to read or write right
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now. curl_multi_perform() returns as soon as the reads/writes are done. This
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function does not require that there actually is any data available for
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reading or that data can be written, it can be called just in case. It will
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write the number of handles that still transfer data in the second argument's
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integer-pointer.
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When you call curl_multi_perform() and the amount of \fIrunning_handles\fP is
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changed from the previous call (or is less than the amount of easy handles
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you've added to the multi handle), you know that there is one or more
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transfers less "running". You can then call \fIcurl_multi_info_read(3)\fP to
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get information about each individual completed transfer, and that returned
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info includes CURLcode and more.
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.SH "RETURN VALUE"
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CURLMcode type, general libcurl multi interface error code.
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If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this basically means that you
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should call \fIcurl_multi_perform\fP again, before you select() on more
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actions. You don't have to do it immediately, but the return code means that
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libcurl may have more data available to return or that there may be more data
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to send off before it is "satisfied". Do note that \fIcurl_multi_perform(3)\fP
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will return \fICURLM_CALL_MULTI_PERFORM\fP only when it wants to be called
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again \fBimmediately\fP. When things are fine and there is nothing immediate
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it wants done, it'll return \fICURLM_OK\fP and you need to wait for \&"action"
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and then call this function again.
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NOTE that this only returns errors etc regarding the whole multi stack. Problems
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still might have occurred on individual transfers even when this
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function returns \fICURLM_OK\fP.
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.SH "TYPICAL USAGE"
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Most applications will use \fIcurl_multi_fdset(3)\fP to get the multi_handle's
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file descriptors, then it'll wait for action on them using \fBselect(3)\fP and
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as soon as one or more of them are ready, \fIcurl_multi_perform(3)\fP gets
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called.
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.SH "SEE ALSO"
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.BR curl_multi_cleanup "(3), " curl_multi_init "(3), "
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.BR curl_multi_fdset "(3), " curl_multi_info_read "(3), "
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.BR libcurl-errors "(3)"
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