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
An unsigned integer type used for the number of file
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
Data other than high-priority data may be read without
Normal data may be read without blocking.
Priority data may be read without blocking.
High priority data may be read without blocking.
Normal data may be written without blocking.
Equivalent to POLLOUT.
Priority data may be written.
An error has occurred ( revents only).
Device has been disconnected ( revents only).
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.
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