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.
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
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
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.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 poll.h(0P)