<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 environments 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 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 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 Technol-
       ogy -- 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 original Standard can  be  obtained
       online at http://www.opengroup.org/unix/online.html .

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