.\" $Id: curl_multi_fdset.3,v 1.11 2005/04/25 08:55:55 bagder Exp $ .\" .TH curl_multi_fdset 3 "25 Apr 2005" "libcurl 7.9.5" "libcurl Manual" .SH NAME curl_multi_fdset - extracts file descriptor information from a multi handle .SH SYNOPSIS .nf #include CURLMcode curl_multi_fdset(CURLM *multi_handle, fd_set *read_fd_set, fd_set *write_fd_set, fd_set *exc_fd_set, int *max_fd); .ad .SH DESCRIPTION This function extracts file descriptor information from a given multi_handle. libcurl returns its fd_set sets. The application can use these to select() on, but be sure to FD_ZERO them before calling this function as \fIcurl_multi_fdset(3)\fP only adds its own descriptors it doesn't zero or otherwise remove any other. The \fIcurl_multi_perform(3)\fP function should be called as soon as one of them are ready to be read from or written to. If no file descriptors are set by libcurl, \fImax_fd\fP will contain -1 when this function returns. Otherwise it will contain the higher descriptor number libcurl set. You should also be aware that when doing select(), you should consider using a rather small (single-digit number of seconds) timeout and call \fIcurl_multi_perform\fP regularly - even if no activity has been seen on the fd_sets - as otherwise libcurl-internal retries and timeouts may not work as you'd think and want. .SH RETURN VALUE CURLMcode type, general libcurl multi interface error code. See \fIlibcurl-errors(3)\fP .SH "SEE ALSO" .BR curl_multi_cleanup "(3)," curl_multi_init "(3)"