poll.h
Section: POSIX Programmer's Manual (0P)
Updated: 2017
Page Index
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.
NAME
poll.h
--- definitions for the poll() function
SYNOPSIS
#include <poll.h>
DESCRIPTION
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.
SEE ALSO
The System Interfaces volume of POSIX.1-2017,
confstr(),
poll()
The Shell and Utilities volume of POSIX.1-2017,
getconf
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
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.opengroup.org/unix/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 .