curl_multi_wait.3: clarify numfds being used if not NULL

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.\" * Copyright (C) 1998 - 2013, Daniel Stenberg, <daniel@haxx.se>, et al.

.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.

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                          int *numfds);

.ad

.SH DESCRIPTION

This function polls on all file descriptors used by the curl easy handles

contained in the given multi handle set.  It will block until activity is

detected on at least one of the handles or \fItimeout_ms\fP has passed.

\fIcurl_multi_wait(3)\fP polls all file descriptors used by the curl easy

handles contained in the given multi handle set.  It will block until activity

is detected on at least one of the handles or \fItimeout_ms\fP has passed.

Alternatively, if the multi handle has a pending internal timeout that has a

shorter expiry time than \fItimeout_ms\fP, that shorter time will be used

instead to make sure timeout accuracy is reasonably kept.

The calling application may pass additional curl_waitfd structures which are

similar to \fIpoll(2)\fP's pollfd structure to be waited on in the same call.

On completion, if \fInumfds\fP is supplied, it will be populated with the

On completion, if \fInumfds\fP is non-NULL, it will be populated with the

total number of file descriptors on which interesting events occured. This

number can include both libcurl internal descriptors as well as descriptors

provided in \fIextra_fds\fP.