IEEE/The Open Group
This manual page is part of the POSIX Programmer’s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
poll.h — definitions for the poll() function
The <poll.h> header shall define the pollfd structure, which shall include at least the following members:
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 significance and semantics of normal, priority, and high-priority data are file and device-specific.
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 <poll.h> header shall define the following symbolic constants, 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 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 POSIX.1-2008, confstr(), poll()
The Shell and Utilities volume of POSIX.1-2008, getconf
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .