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54 lines
2.7 KiB
Groff
54 lines
2.7 KiB
Groff
.\"
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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. If an added handle fails very quickly, it may
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never be counted as a running_handle.
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When \fIrunning_handles\fP is set to zero (0) on the return of this function,
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there is no longer any transfers in progress.
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.SH "RETURN VALUE"
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CURLMcode type, general libcurl multi interface error code.
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Before version 7.20.0: If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this
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basically means that you should call \fIcurl_multi_perform\fP again, before
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you select() on more actions. You don't have to do it immediately, but the
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return code means that libcurl may have more data available to return or that
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there may be more data to send off before it is "satisfied". Do note that
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\fIcurl_multi_perform(3)\fP will return \fICURLM_CALL_MULTI_PERFORM\fP only
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when it wants to be called again \fBimmediately\fP. When things are fine and
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there is nothing immediate it wants done, it'll return \fICURLM_OK\fP and you
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need to wait for \&"action" and then call this function again.
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This function only returns errors etc regarding the whole multi stack.
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Problems 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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