poll.h(7POSIX) POSIX Programmer's Manual poll.h(7POSIX)
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.
poll.h — definitions for the poll() function
The <poll.h> header shall define the pollfd structure, which shall include at least the
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 envi‐
ronments 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
The following shall be declared as a function and may also be defined as a macro. A func‐
tion prototype shall be provided.
int poll(struct pollfd , nfds_t, int);
The following sections are informative.
The System Interfaces volume of POSIX.1‐2008, confstr(), poll()
The Shell and Utilities volume of POSIX.1‐2008, getconf
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 discrep‐
ancy 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 https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 poll.h(7POSIX)