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
header shall define the pollfd
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).
header shall define the following type through
- 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
() function or the getconf
header shall define the following symbolic constants,
zero or more of which may be OR'ed together to form the events
members in the pollfd
- Data other than high-priority data may be read without
- Normal data may be read without blocking.
- Priority data may be read without blocking.
- High priority data may be read without blocking.
- Normal data may be written without blocking.
- Equivalent to POLLOUT.
- Priority data may be written.
- An error has occurred (revents only).
- Device has been disconnected (revents only).
- 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.
The following sections are informative.
int poll(struct pollfd , nfds_t, int);
The System Interfaces volume of POSIX.1‐2008, confstr()
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 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
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