154 lines
5.9 KiB
HTML
154 lines
5.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>ungetwc</title>
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<basefont size="3"> <a name="ungetwc"></a> <a name="tag_03_801"></a><!-- ungetwc -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_801_01"></a>NAME</h4>
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<blockquote>ungetwc - push wide-character code back into the input stream</blockquote>
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<h4><a name="tag_03_801_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/stdio.h.html">stdio.h</a>><br>
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#include <<a href="../basedefs/wchar.h.html">wchar.h</a>><br>
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<br>
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wint_t ungetwc(wint_t</tt> <i>wc</i><tt>, FILE *</tt><i>stream</i><tt>);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_801_03"></a>DESCRIPTION</h4>
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<blockquote>
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<div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"
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border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
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requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to
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the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div>
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<p>The <i>ungetwc</i>() function shall push the character corresponding to the wide-character code specified by <i>wc</i> back onto
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the input stream pointed to by <i>stream</i>. The pushed-back characters shall be returned by subsequent reads on that stream in
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the reverse order of their pushing. A successful intervening call (with the stream pointed to by <i>stream</i>) to a
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file-positioning function ( <a href="../functions/fseek.html"><i>fseek</i>()</a>, <a href=
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"../functions/fsetpos.html"><i>fsetpos</i>()</a>, or <a href="../functions/rewind.html"><i>rewind</i>()</a>) discards any
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pushed-back characters for the stream. The external storage corresponding to the stream is unchanged.</p>
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<p>At least one character of push-back shall be provided. If <i>ungetwc</i>() is called too many times on the same stream without
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an intervening read or file-positioning operation on that stream, the operation may fail.</p>
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<p>If the value of <i>wc</i> equals that of the macro WEOF, the operation shall fail and the input stream shall be left
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unchanged.</p>
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<p>A successful call to <i>ungetwc</i>() shall clear the end-of-file indicator for the stream. The value of the file-position
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indicator for the stream after reading or discarding all pushed-back characters shall be the same as it was before the characters
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were pushed back. The file-position indicator is decremented (by one or more) by each successful call to <i>ungetwc</i>(); if its
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value was 0 before a call, its value is unspecified after the call.</p>
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</blockquote>
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<h4><a name="tag_03_801_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, <i>ungetwc</i>() shall return the wide-character code corresponding to the pushed-back character.
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Otherwise, it shall return WEOF.</p>
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</blockquote>
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<h4><a name="tag_03_801_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>ungetwc</i>() function may fail if:</p>
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<dl compact>
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<dt>[EILSEQ]</dt>
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<dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> An
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invalid character sequence is detected, or a wide-character code does not correspond to a valid character. <img src=
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"../images/opt-end.gif" alt="[Option End]" border="0"></dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_801_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_801_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_801_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_801_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_801_10"></a>SEE ALSO</h4>
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<blockquote>
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<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> ,
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<a href="rewind.html"><i>rewind</i>()</a> , <a href="setbuf.html"><i>setbuf</i>()</a> , the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/stdio.h.html"><i><stdio.h></i></a>, <a href=
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"../basedefs/wchar.h.html"><i><wchar.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_801_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 4. Derived from the MSE working draft.</p>
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</blockquote>
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<h4><a name="tag_03_801_12"></a>Issue 5</h4>
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<blockquote>
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<p>The Optional Header (OH) marking is removed from <a href="../basedefs/stdio.h.html"><i><stdio.h></i></a>.</p>
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</blockquote>
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<h4><a name="tag_03_801_13"></a>Issue 6</h4>
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<blockquote>
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<p>The [EILSEQ] optional error condition is marked CX.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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UNIX ® is a registered Trademark of The Open Group.<br>
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