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| .TH curl_multi_perform 3 "1 March 2002" "libcurl 7.9.5" "libcurl Manual" |
| .SH NAME |
| curl_multi_perform - reads/writes available data from each easy handle |
| .SH SYNOPSIS |
| #include <curl/curl.h> |
| |
| CURLMcode curl_multi_perform(CURLM *multi_handle, int *running_handles); |
| .ad |
| .SH DESCRIPTION |
| When the app thinks there's data available for the multi_handle, it should |
| call this function to read/write whatever there is to read or write right |
| now. curl_multi_perform() returns as soon as the reads/writes are done. This |
| function does not require that there actually is any data available for |
| reading or that data can be written, it can be called just in case. It will |
| write the number of handles that still transfer data in the second argument's |
| integer-pointer. |
| |
| When you call curl_multi_perform() and the amount of \fIrunning_handles\fP is |
| changed from the previous call (or is less than the amount of easy handles |
| you've added to the multi handle), you know that there is one or more |
| transfers less "running". You can then call \fIcurl_multi_info_read(3)\fP to |
| get information about each individual completed transfer, and that returned |
| info includes CURLcode and more. If an added handle fails very quickly, it may |
| never be counted as a running_handle. |
| |
| When \fIrunning_handles\fP is set to zero (0) on the return of this function, |
| there is no longer any transfers in progress. |
| .SH "RETURN VALUE" |
| CURLMcode type, general libcurl multi interface error code. |
| |
| Before version 7.20.0: If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this |
| basically means that you should call \fIcurl_multi_perform\fP again, before |
| you select() on more actions. You don't have to do it immediately, but the |
| return code means that libcurl may have more data available to return or that |
| there may be more data to send off before it is "satisfied". Do note that |
| \fIcurl_multi_perform(3)\fP will return \fICURLM_CALL_MULTI_PERFORM\fP only |
| when it wants to be called again \fBimmediately\fP. When things are fine and |
| there is nothing immediate it wants done, it'll return \fICURLM_OK\fP and you |
| need to wait for \&"action" and then call this function again. |
| |
| This function only returns errors etc regarding the whole multi stack. |
| Problems still might have occurred on individual transfers even when this |
| function returns \fICURLM_OK\fP. |
| .SH "TYPICAL USAGE" |
| Most applications will use \fIcurl_multi_fdset(3)\fP to get the multi_handle's |
| file descriptors, then it'll wait for action on them using \fBselect(3)\fP and |
| as soon as one or more of them are ready, \fIcurl_multi_perform(3)\fP gets |
| called. |
| .SH "SEE ALSO" |
| .BR curl_multi_cleanup "(3), " curl_multi_init "(3), " |
| .BR curl_multi_fdset "(3), " curl_multi_info_read "(3), " |
| .BR libcurl-errors "(3)" |
