poll.h - definitions for the poll() function
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
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.
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.
int poll(struct pollfd, nfds_t, int);
The following sections are informative.
The System Interfaces volume of IEEE Std 1003.1-2001, confstr(),
poll(), the Shell and Utilities volume of IEEE Std 1003.1-2001, getconf
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 .