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



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  get-
       conf 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 Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                  <poll.h>(0P)