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<poll.h>(P)			    POSIX Programmer's Manual			      <poll.h>(P)

NAME
       poll.h - definitions for the poll() function

SYNOPSIS
       #include <poll.h>

DESCRIPTION
       The <poll.h> header shall define the pollfd structure that includes 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 envi-
       ronments can be obtained using the confstr() function or the getconf utility.

       The following symbolic constants shall be defined, 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  func-
       tion 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 IEEE Std 1003.1-2001, confstr(), poll(), the Shell and
       Utilities volume of IEEE Std 1003.1-2001, getconf

COPYRIGHT
       Portions of this text are reprinted and	reproduced  in	electronic  form  from	IEEE  Std
       1003.1,	2003  Edition,	Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				      <poll.h>(P)
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