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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><sys/uio.h></title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../../jscript/dotcode.js"></script><basefont size="3"> <a name="<sys/uio.h>"></a> <a name="tag_13_68"></a><!-- <sys/uio.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_68_01"></a>NAME</h4><blockquote>sys/uio.h - definitions for vector I/O operations</blockquote><h4><a name="tag_13_68_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 <sys/uio.h> <img src="../../images/opt-end.gif" alt="[Option End]" border="0"></tt></div></blockquote><h4><a name="tag_13_68_03"></a>DESCRIPTION</h4><blockquote><p>The <i><sys/uio.h></i> header shall define the <b>iovec</b> structure that includes at least the following members:</p><pre><tt>void *iov_base </tt> Base address of a memory region for input or output. <tt>size_t iov_len </tt> The size of the memory pointed to by <i>iov_base.</i> <tt></tt></pre><p>The <i><sys/uio.h></i> header uses the <b>iovec</b> structure for scatter/gather I/O.</p><p>The <b>ssize_t</b> and <b>size_t</b> types shall be defined as described in <a href="../../basedefs/sys/types.h.html"><i><sys/types.h></i></a>.</p><p>The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.</p><pre><tt>ssize_t readv(int, const struct iovec *, int);ssize_t writev(int, const struct iovec *, int);</tt></pre></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_13_68_04"></a>APPLICATION USAGE</h4><blockquote><p>The implementation can put a limit on the number of scatter/gather elements which can be processed in one call. The symbol{IOV_MAX} defined in <a href="../../basedefs/limits.h.html"><i><limits.h></i></a> should always be used to learn about thelimits instead of assuming a fixed value.</p></blockquote><h4><a name="tag_13_68_05"></a>RATIONALE</h4><blockquote><p>Traditionally, the maximum number of scatter/gather elements the system can process in one call were described by the symbolicvalue {UIO_MAXIOV}. In IEEE Std 1003.1-2001 this value is replaced by the constant {IOV_MAX} which can be found in <ahref="../../basedefs/limits.h.html"><i><limits.h></i></a>.</p></blockquote><h4><a name="tag_13_68_06"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_68_07"></a>SEE ALSO</h4><blockquote><p><a href="../limits.h.html#tag_13_24"><i><limits.h></i></a> , <a href="../sys/types.h.html#tag_13_67"><i><sys/types.h></i></a> , the System Interfaces volume of IEEE Std 1003.1-2001, <ahref="../../functions/read.html"><i>read</i>()</a>, <a href="../../functions/write.html"><i>write</i>()</a></p></blockquote><h4><a name="tag_13_68_08"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 4, Version 2.</p></blockquote><h4><a name="tag_13_68_09"></a>Issue 6</h4><blockquote><p>Text referring to scatter/gather I/O is added to the DESCRIPTION.</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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