266 lines
9.9 KiB
HTML
266 lines
9.9 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>unexpand</title>
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<basefont size="3"> <a name="unexpand"></a> <a name="tag_04_156"></a><!-- unexpand -->
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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_04_156_01"></a>NAME</h4>
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<blockquote>unexpand - convert spaces to tabs</blockquote>
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<h4><a name="tag_04_156_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('UP')">UP</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> unexpand</tt> <b>[</b> <tt>-a| -t</tt> <i>tablist</i><b>][</b><i>file</i><tt>...</tt><b>]</b><tt><img
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src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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</blockquote>
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<h4><a name="tag_04_156_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>unexpand</i> utility shall copy files or standard input to standard output, converting <blank>s at the beginning of
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each line into the maximum number of <tab>s followed by the minimum number of <space>s needed to fill the same column
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positions originally filled by the translated <blank>s. By default, tabstops shall be set at every eighth column position.
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Each <backspace> shall be copied to the output, and shall cause the column position count for tab calculations to be
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decremented; the count shall never be decremented to a value less than one.</p>
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</blockquote>
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<h4><a name="tag_04_156_04"></a>OPTIONS</h4>
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<blockquote>
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<p>The <i>unexpand</i> utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/xbd_chap12.html#tag_12_02">Section 12.2, Utility Syntax Guidelines</a>.</p>
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<p>The following options shall be supported:</p>
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<dl compact>
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<dt><b>-a</b></dt>
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<dd>In addition to translating <blank>s at the beginning of each line, translate all sequences of two or more <blank>s
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immediately preceding a tab stop to the maximum number of <tab>s followed by the minimum number of <space>s needed to
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fill the same column positions originally filled by the translated <blank>s.</dd>
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<dt><b>-t </b> <i>tablist</i></dt>
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<dd>Specify the tab stops. The application shall ensure that the <i>tablist</i> option-argument is a single argument consisting of
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a single positive decimal integer or multiple positive decimal integers, separated by <blank>s or commas, in ascending order.
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If a single number is given, tabs shall be set <i>tablist</i> column positions apart instead of the default 8. If multiple numbers
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are given, the tabs shall be set at those specific column positions.
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<p>The application shall ensure that each tab-stop position <i>N</i> is an integer value greater than zero, and the list shall be
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in strictly ascending order. This is taken to mean that, from the start of a line of output, tabbing to position <i>N</i> shall
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cause the next character output to be in the ( <i>N</i>+1)th column position on that line. When the <b>-t</b> option is not
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specified, the default shall be the equivalent of specifying <b>-t 8</b> (except for the interaction with <b>-a</b>, described
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below).</p>
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<p>No <space>-to- <tab> conversions shall occur for characters at positions beyond the last of those specified in a
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multiple tab-stop list.</p>
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<p>When <b>-t</b> is specified, the presence or absence of the <b>-a</b> option shall be ignored; conversion shall not be limited
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to the processing of leading <blank>s.</p>
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</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_156_05"></a>OPERANDS</h4>
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<blockquote>
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<p>The following operand shall be supported:</p>
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<dl compact>
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<dt><i>file</i></dt>
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<dd>A pathname of a text file to be used as input.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_156_06"></a>STDIN</h4>
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<blockquote>
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<p>See the INPUT FILES section.</p>
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</blockquote>
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<h4><a name="tag_04_156_07"></a>INPUT FILES</h4>
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<blockquote>
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<p>The input files shall be text files.</p>
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</blockquote>
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<h4><a name="tag_04_156_08"></a>ENVIRONMENT VARIABLES</h4>
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<blockquote>
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<p>The following environment variables shall affect the execution of <i>unexpand</i>:</p>
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<dl compact>
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<dt><i>LANG</i></dt>
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<dd>Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html#tag_08_02">Section 8.2, Internationalization Variables</a> for
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the precedence of internationalization variables used to determine the values of locale categories.)</dd>
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<dt><i>LC_ALL</i></dt>
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<dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd>
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<dt><i>LC_CTYPE</i></dt>
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<dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as
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opposed to multi-byte characters in arguments and input files), the processing of <tab>s and <space>s, and for the
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determination of the width in column positions each character would occupy on an output device.</dd>
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<dt><i>LC_MESSAGES</i></dt>
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<dd>Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard
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error.</dd>
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<dt><i>NLSPATH</i></dt>
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<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Determine the location of message catalogs for the processing of <i>LC_MESSAGES .</i> <img src="../images/opt-end.gif" alt=
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"[Option End]" border="0"></dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_156_09"></a>ASYNCHRONOUS EVENTS</h4>
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<blockquote>
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<p>Default.</p>
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</blockquote>
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<h4><a name="tag_04_156_10"></a>STDOUT</h4>
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<blockquote>
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<p>The standard output shall be equivalent to the input files with the specified <space>-to- <tab> conversions.</p>
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</blockquote>
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<h4><a name="tag_04_156_11"></a>STDERR</h4>
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<blockquote>
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<p>The standard error shall be used only for diagnostic messages.</p>
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</blockquote>
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<h4><a name="tag_04_156_12"></a>OUTPUT FILES</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_04_156_13"></a>EXTENDED DESCRIPTION</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_04_156_14"></a>EXIT STATUS</h4>
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<blockquote>
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<p>The following exit values shall be returned:</p>
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<dl compact>
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<dt> 0</dt>
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<dd>Successful completion.</dd>
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<dt>>0</dt>
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<dd>An error occurred.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_156_15"></a>CONSEQUENCES OF ERRORS</h4>
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<blockquote>
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<p>Default.</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_04_156_16"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>One non-intuitive aspect of <i>unexpand</i> is its restriction to leading spaces when neither <b>-a</b> nor <b>-t</b> is
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specified. Users who always want to convert all spaces in a file can easily alias <i>unexpand</i> to use the <b>-a</b> or
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<b>-t 8</b> option.</p>
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</blockquote>
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<h4><a name="tag_04_156_17"></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_04_156_18"></a>RATIONALE</h4>
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<blockquote>
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<p>On several occasions, consideration was given to adding a <b>-t</b> option to the <i>unexpand</i> utility to complement the
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<b>-t</b> in <a href="../utilities/expand.html"><i>expand</i></a> (see <a href="expand.html"><i>expand</i></a> ). The historical
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intent of <i>unexpand</i> was to translate multiple <blank>s into tab stops, where tab stops were a multiple of eight column
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positions on most UNIX systems. An early proposal omitted <b>-t</b> because it seemed outside the scope of the User Portability
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Utilities option; it was not described in any of the base documents. However, hard-coding tab stops every eight columns was not
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suitable for the international community and broke historical precedents for some vendors in the FORTRAN community, so <b>-t</b>
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was restored in conjunction with the list of valid extension categories considered by the standard developers. Thus,
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<i>unexpand</i> is now the logical converse of <a href="../utilities/expand.html"><i>expand</i></a>.</p>
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</blockquote>
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<h4><a name="tag_04_156_19"></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_04_156_20"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="expand.html"><i>expand</i></a> , <a href="tabs.html"><i>tabs</i></a></p>
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</blockquote>
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<h4><a name="tag_04_156_21"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 4.</p>
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</blockquote>
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<h4><a name="tag_04_156_22"></a>Issue 6</h4>
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<blockquote>
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<p>This utility is marked as part of the User Portability Utilities option.</p>
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<p>The definition of the <i>LC_CTYPE</i> environment variable is changed to align with the IEEE P1003.2b draft standard.</p>
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<p>The normative text is reworded to avoid use of the term "must" for application requirements.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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<hr>
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POSIX ® is a registered Trademark of The IEEE.<br>
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