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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) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>ungetwc</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="ungetwc"></a> <a name="tag_03_801"></a><!-- ungetwc --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_801_01"></a>NAME</h4><blockquote>ungetwc - push wide-character code back into the input stream</blockquote><h4><a name="tag_03_801_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/stdio.h.html">stdio.h</a>><br> #include <<a href="../basedefs/wchar.h.html">wchar.h</a>><br><br> wint_t ungetwc(wint_t</tt> <i>wc</i><tt>, FILE *</tt><i>stream</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_801_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>ungetwc</i>() function shall push the character corresponding to the wide-character code specified by <i>wc</i> back ontothe input stream pointed to by <i>stream</i>. The pushed-back characters shall be returned by subsequent reads on that stream inthe reverse order of their pushing. A successful intervening call (with the stream pointed to by <i>stream</i>) to afile-positioning function ( <a href="../functions/fseek.html"><i>fseek</i>()</a>, <a href="../functions/fsetpos.html"><i>fsetpos</i>()</a>, or <a href="../functions/rewind.html"><i>rewind</i>()</a>) discards anypushed-back characters for the stream. The external storage corresponding to the stream is unchanged.</p><p>At least one character of push-back shall be provided. If <i>ungetwc</i>() is called too many times on the same stream withoutan intervening read or file-positioning operation on that stream, the operation may fail.</p><p>If the value of <i>wc</i> equals that of the macro WEOF, the operation shall fail and the input stream shall be leftunchanged.</p><p>A successful call to <i>ungetwc</i>() shall clear the end-of-file indicator for the stream. The value of the file-positionindicator for the stream after reading or discarding all pushed-back characters shall be the same as it was before the characterswere pushed back. The file-position indicator is decremented (by one or more) by each successful call to <i>ungetwc</i>(); if itsvalue was 0 before a call, its value is unspecified after the call.</p></blockquote><h4><a name="tag_03_801_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>ungetwc</i>() shall return the wide-character code corresponding to the pushed-back character.Otherwise, it shall return WEOF.</p></blockquote><h4><a name="tag_03_801_05"></a>ERRORS</h4><blockquote><p>The <i>ungetwc</i>() function may fail if:</p><dl compact><dt>[EILSEQ]</dt><dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> Aninvalid character sequence is detected, or a wide-character code does not correspond to a valid character. <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_801_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_801_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_801_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_801_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_801_10"></a>SEE ALSO</h4><blockquote><p><a href="fseek.html"><i>fseek</i>()</a>, <a href="fsetpos.html"><i>fsetpos</i>()</a>, <a href="read.html"><i>read</i>()</a>,<a href="rewind.html"><i>rewind</i>()</a>, <a href="setbuf.html"><i>setbuf</i>()</a>, the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/stdio.h.html"><i><stdio.h></i></a>, <a href="../basedefs/wchar.h.html"><i><wchar.h></i></a></p></blockquote><h4><a name="tag_03_801_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 4. Derived from the MSE working draft.</p></blockquote><h4><a name="tag_03_801_12"></a>Issue 5</h4><blockquote><p>The Optional Header (OH) marking is removed from <a href="../basedefs/stdio.h.html"><i><stdio.h></i></a>.</p></blockquote><h4><a name="tag_03_801_13"></a>Issue 6</h4><blockquote><p>The [EILSEQ] optional error condition is marked CX.</p></blockquote><div class="box"><em>End of informative text.</em></div><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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