poll.h(0p)

Usage

#include <poll.h>

Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Overview

The <poll.h> header shall define the pollfd structure, which shall include at least the following members:

int    fd       The following descriptor being polled.
short  events   The input event flags (see below).
short  revents  The output event flags (see below).

The <poll.h> header shall define the following type through typedef:

nfds_t: An unsigned integer type used for the number of file descriptors.

The implementation shall support one or more programming environments in which the width of nfds_t is no greater than the width of type long. The names of these programming environments can be obtained using the confstr() function or the getconf utility.

The <poll.h> header shall define the following symbolic constants, zero or more of which may be OR'ed together to form the events or revents members in the pollfd structure:

`POLLIN`	Data other than high-priority data may be read without blocking.
`POLLRDNORM`	Normal data may be read without blocking.
`POLLRDBAND`	Priority data may be read without blocking.
`POLLPRI`	High priority data may be read without blocking.
`POLLOUT`	Normal data may be written without blocking.
`POLLWRNORM`	Equivalent to POLLOUT.
`POLLWRBAND`	Priority data may be written.
`POLLERR`	An error has occurred (revents only).
`POLLHUP`	Device has been disconnected (revents only).
`POLLNVAL`	Invalid fd member (revents only).

The significance and semantics of normal, priority, and high-priority data are file and device-specific.

The following shall be declared as a function and may also be defined as a macro. A function prototype shall be provided.

int   poll(struct pollfd [], nfds_t, int);

The following sections are informative.

Application usage

None.

Rationale

None.

Future directions

None.