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 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
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .