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.TH zmq_poll 3 "" "(c)2007-2009 FastMQ Inc." "0MQ User Manuals"
.SH NAME
zmq_poll \- polls for events on a set of 0MQ and POSIX sockets
.SH SYNOPSIS
.B int zmq_poll (zmq_pollitem_t *items, int nitems, long timeout);
.SH DESCRIPTION
Waits for the events specified by
.IR items
parameter. Number of items in the array is determined by
.IR nitems
argument. Each item in the array looks like this:
.nf
typedef struct
{
void *socket;
int fd;
short events;
short revents;
} zmq_pollitem_t;
.fi
0MQ socket to poll on is specified by
.IR socket .
In case you want to poll on standard POSIX socket, set
.IR socket
to NULL and fill the POSIX file descriptor to
.IR fd .
.IR events
specifies which events to wait for. It's a combination of the values below.
Once the call exits,
.IR revent
will be filled with events that have actually occured on the socket. The field
will contain a combination of the values below.
.IP "\fBZMQ_POLLIN\fP"
poll for incoming messages.
.IP "\fBZMQ_POLLOUT\fP"
wait while message can be set socket. Poll will return if a message of at least
one byte can be written to the socket. However, there is no guarantee that
arbitrarily large message can be sent.
.IR timeout
argument specifies an upper limit on the time for which
.IR zmq_poll
will block, in microseconds. Specifying a negative value in timeout means
an infinite timeout.
.SH RETURN VALUE
Function returns number of items signaled or -1 in the case of error.
.SH ERRORS
.IP "\fBEFAULT\fP"
there's a 0MQ socket in the pollset belonging to a different application thread.
.IP "\fBENOTSUP\fP"
0MQ context was initialised without ZMQ_POLL flag. I/O multiplexing is disabled.
.SH EXAMPLE
.nf
zmq_pollitem_t items [2];
items [0].socket = s;
items [0].events = ZMQ_POLLIN;
items [1].socket = NULL;
items [1].fd = my_fd;
items [1].events = ZMQ_POLLIN;
int rc = zmq_poll (items, 2);
assert (rc != -1);
.fi
.SH SEE ALSO
.BR zmq_socket (3)
.SH AUTHOR
Martin Sustrik <sustrik at 250bpm dot com>
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