132 lines
5.1 KiB
HTML
132 lines
5.1 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 -->
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>ungetc</title>
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</head>
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<body bgcolor="white">
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<script type="text/javascript" language="JavaScript" src="../jscript/codes.js">
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</script>
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<basefont size="3"> <a name="ungetc"></a> <a name="tag_03_800"></a><!-- ungetc -->
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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_800_01"></a>NAME</h4>
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<blockquote>ungetc - push byte back into input stream</blockquote>
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<h4><a name="tag_03_800_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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<br>
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int ungetc(int</tt> <i>c</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_800_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>ungetc</i>() function shall push the byte specified by <i>c</i> (converted to an <b>unsigned char</b>) back onto the
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input stream pointed to by <i>stream</i>. The pushed-back bytes shall be returned by subsequent reads on that stream in the reverse
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order of their pushing. A successful intervening call (with the stream pointed to by <i>stream</i>) to a file-positioning function
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( <a href="../functions/fseek.html"><i>fseek</i>()</a>, <a href="../functions/fsetpos.html"><i>fsetpos</i>()</a>, or <a href=
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"../functions/rewind.html"><i>rewind</i>()</a>) shall discard any pushed-back bytes for the stream. The external storage
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corresponding to the stream shall be unchanged.</p>
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<p>One byte of push-back shall be provided. If <i>ungetc</i>() is called too many times on the same stream without an intervening
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read or file-positioning operation on that stream, the operation may fail.</p>
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<p>If the value of <i>c</i> equals that of the macro EOF, 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>ungetc</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 bytes shall be the same as it was before the bytes were pushed
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back. The file-position indicator is decremented by each successful call to <i>ungetc</i>(); if its value was 0 before a call, its
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value is unspecified after the call.</p>
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</blockquote>
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<h4><a name="tag_03_800_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, <i>ungetc</i>() shall return the byte pushed back after conversion. Otherwise, it shall return
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EOF.</p>
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</blockquote>
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<h4><a name="tag_03_800_05"></a>ERRORS</h4>
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<blockquote>
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<p>No errors are defined.</p>
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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_800_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_800_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_800_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_800_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_800_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="getc.html"><i>getc</i>()</a> , <a href="fsetpos.html"><i>fsetpos</i>()</a> ,
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<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
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Base Definitions volume of IEEE Std 1003.1-2001, <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_800_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 1. Derived from Issue 1 of the SVID.</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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POSIX ® is a registered Trademark of The IEEE.<br>
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