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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title><poll.h></title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_007_982"> </a>NAME</h4><blockquote>poll.h - definitions for the poll() function</blockquote><h4><a name = "tag_000_007_983"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <poll.h></code></pre></blockquote><h4><a name = "tag_000_007_984"> </a>DESCRIPTION</h4><blockquote>The<i><poll.h></i>header defines the<b>pollfd</b>structure that includes at least the following member:<pre><code>int fd the following descriptor being polledshort int events the input event flags (see below)short int revents the output event flags (see below)</code></pre><p>The<i><poll.h></i>header defines the following type through typedef:<dl compact><dt><b>nfds_t</b><dd>An unsigned integral type used for the number of file descriptors.</dl><p>The following symbolic constants are defined, zero or more ofwhich may be OR-ed together to form the <b>events</b> or<b>revents</b> members in the <b>pollfd</b> structure:<dl compact><dt>POLLIN<dd>Same effect as POLLRDNORM | POLLRDBAND.<dt>POLLRDNORM<dd>Data on priority band 0 may be read.<dt>POLLRDBAND<dd>Data on priority bands greater than 0 may be read.<dt>POLLPRI<dd>High priority data may be read.<dt>POLLOUT<dd>Same value as POLLWRNORM.<dt>POLLWRNORM<dd>Data on priority band 0 may be written.<dt>POLLWRBAND<dd>Data on priority bands greater than 0 may be written.This event only examines bands that have been written to at leastonce.<dt>POLLERR<dd>An error has occurred (<b>revents</b> only).<dt>POLLHUP<dd>Device has been disconnected (<b>revents</b> only).<dt>POLLNVAL<dd>Invalid <b>fd</b> member (<b>revents</b> only).</dl><p>The <<b>poll.h</b>> header declares the following function whichmay also be defined as a macro.Function prototypes must be provided for use with an ISO Ccompiler.<pre><code>int <a href="poll.html">poll</a>(struct pollfd[], nfds_t, int);</code></pre></blockquote><h4><a name = "tag_000_007_985"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_986"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_987"> </a>SEE ALSO</h4><blockquote><i><a href="poll.html">poll()</a></i>.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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