📄 setvbuf.html
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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>setvbuf</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="setvbuf"></a> <a name="tag_03_672"></a><!-- setvbuf --> <!--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_03_672_01"></a>NAME</h4><blockquote>setvbuf - assign buffering to a stream</blockquote><h4><a name="tag_03_672_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/stdio.h.html">stdio.h</a>><br><br> int setvbuf(FILE *restrict</tt> <i>stream</i><tt>, char *restrict</tt> <i>buf</i><tt>, int</tt> <i>type</i><tt>,<br> size_t</tt> <i>size</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_672_03"></a>DESCRIPTION</h4><blockquote><div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between therequirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers tothe ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div><p>The <i>setvbuf</i>() function may be used after the stream pointed to by <i>stream</i> is associated with an open file butbefore any other operation (other than an unsuccessful call to <i>setvbuf</i>()) is performed on the stream. The argument<i>type</i> determines how <i>stream</i> shall be buffered, as follows:</p><ul><li><p>{_IOFBF} shall cause input/output to be fully buffered.</p></li><li><p>{_IOLBF} shall cause input/output to be line buffered.</p></li><li><p>{_IONBF} shall cause input/output to be unbuffered.</p></li></ul><p>If <i>buf</i> is not a null pointer, the array it points to may be used instead of a buffer allocated by <i>setvbuf</i>() andthe argument <i>size</i> specifies the size of the array; otherwise, <i>size</i> may determine the size of a buffer allocated bythe <i>setvbuf</i>() function. The contents of the array at any time are unspecified.</p><p>For information about streams, see <a href="xsh_chap02_05.html#tag_02_05"><i>Standard I/O Streams</i></a> .</p></blockquote><h4><a name="tag_03_672_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>setvbuf</i>() shall return 0. Otherwise, it shall return a non-zero value if an invalid value isgiven for <i>type</i> or if the request cannot be honored, <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and may set <i>errno</i> to indicate the error. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_672_05"></a>ERRORS</h4><blockquote><p>The <i>setvbuf</i>() function may fail if:</p><dl compact><dt>[EBADF]</dt><dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The file descriptor underlying <i>stream</i> is not valid. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_672_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_672_07"></a>APPLICATION USAGE</h4><blockquote><p>A common source of error is allocating buffer space as an "automatic" variable in a code block, and then failing to close thestream in the same block.</p><p>With <i>setvbuf</i>(), allocating a buffer of <i>size</i> bytes does not necessarily imply that all of <i>size</i> bytes areused for the buffer area.</p><p>Applications should note that many implementations only provide line buffering on input from terminal devices.</p></blockquote><h4><a name="tag_03_672_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_672_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_672_10"></a>SEE ALSO</h4><blockquote><p><a href="xsh_chap02_05.html#tag_02_05"><i>Standard I/O Streams</i></a> , <a href="fopen.html"><i>fopen</i>()</a> , <a href="setbuf.html"><i>setbuf</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/stdio.h.html"><i><stdio.h></i></a></p></blockquote><h4><a name="tag_03_672_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><h4><a name="tag_03_672_12"></a>Issue 6</h4><blockquote><p>Extensions beyond the ISO C standard are marked.</p><p>The <i>setvbuf</i>() prototype is updated for alignment with the ISO/IEC 9899:1999 standard.</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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