poll.h(0P)		   POSIX Programmer's Manual		    poll.h(0P)

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 .

IEEE/The Open Group		     2017			    poll.h(0P)