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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title><poll.h></title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="<poll.h>"></a> <a name="tag_13_35"></a><!-- <poll.h> --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_13_35_01"></a>NAME</h4><blockquote>poll.h - definitions for the poll() function</blockquote><h4><a name="tag_13_35_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <poll.h> <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></div></blockquote><h4><a name="tag_13_35_03"></a>DESCRIPTION</h4><blockquote><p>The <i><poll.h></i> header shall define the <b>pollfd</b> structure that includes at least the following members:</p><pre><tt>int fd </tt> The following descriptor being polled. <tt>short events </tt> The input event flags (see below). <tt>short revents </tt> The output event flags (see below). <tt></tt></pre><p>The <i><poll.h></i> header shall define the following type through <b>typedef</b>:</p><dl compact><dt><b>nfds_t</b></dt><dd>An unsigned integer type used for the number of file descriptors.</dd></dl><p>The implementation shall support one or more programming environments in which the width of <b>nfds_t</b> is no greater than thewidth of type <b>long</b>. The names of these programming environments can be obtained using the <a href="../functions/confstr.html"><i>confstr</i>()</a> function or the <a href="../utilities/getconf.html"><i>getconf</i></a>utility.</p><p>The following symbolic constants shall be defined, zero or more of which may be OR'ed together to form the <i>events</i> or<i>revents</i> members in the <b>pollfd</b> structure:</p><dl compact><dt>POLLIN</dt><dd>Data other than high-priority data may be read without blocking.</dd><dt>POLLRDNORM</dt><dd>Normal data may be read without blocking.</dd><dt>POLLRDBAND</dt><dd>Priority data may be read without blocking.</dd><dt>POLLPRI</dt><dd>High priority data may be read without blocking.</dd><dt>POLLOUT</dt><dd>Normal data may be written without blocking.</dd><dt>POLLWRNORM</dt><dd>Equivalent to POLLOUT.</dd><dt>POLLWRBAND</dt><dd>Priority data may be written.</dd><dt>POLLERR</dt><dd>An error has occurred ( <i>revents</i> only).</dd><dt>POLLHUP</dt><dd>Device has been disconnected ( <i>revents</i> only).</dd><dt>POLLNVAL</dt><dd>Invalid <i>fd</i> member ( <i>revents</i> only).</dd></dl><p>The significance and semantics of normal, priority, and high-priority data are file and device-specific.</p><p>The following shall be declared as a function and may also be defined as a macro. A function prototype shall be provided.</p><pre><tt>int poll(struct pollfd[], nfds_t, int);</tt></pre></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_13_35_04"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_35_05"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_35_06"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_35_07"></a>SEE ALSO</h4><blockquote><p>The System Interfaces volume of IEEE Std 1003.1-2001, <a href="../functions/confstr.html"><i>confstr</i>()</a>, <ahref="../functions/poll.html"><i>poll</i>()</a>, the Shell and Utilities volume of IEEE Std 1003.1-2001, <a href="../utilities/getconf.html"><i>getconf</i></a></p></blockquote><h4><a name="tag_13_35_08"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 4, Version 2.</p></blockquote><h4><a name="tag_13_35_09"></a>Issue 6</h4><blockquote><p>The description of the symbolic constants is updated to match the <a href="../functions/poll.html"><i>poll</i>()</a>function.</p><p>Text related to STREAMS has been moved to the <a href="../functions/poll.html"><i>poll</i>()</a> reference page.</p><p>A note is added to the DESCRIPTION regarding the significance and semantics of normal, priority, and high-priority data.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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