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 .
