289 lines
8.8 KiB
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289 lines
8.8 KiB
HTML
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<title>alias</title>
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<basefont size="3"> <a name="alias"></a> <a name="tag_04_02"></a><!-- alias -->
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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_02_01"></a>NAME</h4>
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<blockquote>alias - define or display aliases</blockquote>
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<h4><a name="tag_04_02_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"> alias</tt> <b>[</b><i>alias-name</i><b>[</b><tt>=</tt><i>string</i><b>]</b>
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<tt>...</tt><b>]</b><tt><img 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_02_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>alias</i> utility shall create or redefine alias definitions or write the values of existing alias definitions to
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standard output. An alias definition provides a string value that shall replace a command name when it is encountered; see <a href=
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"xcu_chap02.html#tag_02_03_01"><i>Alias Substitution</i></a> .</p>
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<p>An alias definition shall affect the current shell execution environment and the execution environments of the subshells of the
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current shell. When used as specified by this volume of IEEE Std 1003.1-2001, the alias definition shall not affect the
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parent process of the current shell nor any utility environment invoked by the shell; see <a href=
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"xcu_chap02.html#tag_02_12"><i>Shell Execution Environment</i></a> .</p>
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</blockquote>
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<h4><a name="tag_04_02_04"></a>OPTIONS</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_02_05"></a>OPERANDS</h4>
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<blockquote>
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<p>The following operands shall be supported:</p>
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<dl compact>
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<dt><i>alias-name</i></dt>
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<dd>Write the alias definition to standard output.</dd>
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<dt><i>alias-name</i>=<i>string</i></dt>
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<dd><br>
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Assign the value of <i>string</i> to the alias <i>alias-name</i>.</dd>
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</dl>
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<p>If no operands are given, all alias definitions shall be written to standard output.</p>
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</blockquote>
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<h4><a name="tag_04_02_06"></a>STDIN</h4>
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<blockquote>
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<p>Not used.</p>
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</blockquote>
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<h4><a name="tag_04_02_07"></a>INPUT 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_02_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>alias</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).</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_02_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_02_10"></a>STDOUT</h4>
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<blockquote>
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<p>The format for displaying aliases (when no operands or only <i>name</i> operands are specified) shall be:</p>
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<pre>
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<tt>"%s=%s\n",</tt> <i>name</i><tt>,</tt> <i>value</i>
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</pre>
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<p>The <i>value</i> string shall be written with appropriate quoting so that it is suitable for reinput to the shell. See the
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description of shell quoting in <a href="xcu_chap02.html#tag_02_02"><i>Quoting</i></a> .</p>
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</blockquote>
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<h4><a name="tag_04_02_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_02_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_02_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_02_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>One of the <i>name</i> operands specified did not have an alias definition, or an error occurred.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_02_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_02_16"></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_04_02_17"></a>EXAMPLES</h4>
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<blockquote>
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<ol>
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<li>
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<p>Change <a href="../utilities/ls.html"><i>ls</i></a> to give a columnated, more annotated output:</p>
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<pre>
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<tt>alias ls="ls -CF"
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</tt>
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</pre>
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</li>
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<li>
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<p>Create a simple "redo" command to repeat previous entries in the command history file:</p>
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<pre>
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<tt>alias r='fc -s'
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</tt>
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</pre>
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</li>
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<li>
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<p>Use 1K units for <a href="../utilities/du.html"><i>du</i></a>:</p>
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<pre>
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<tt>alias du=du\ -k
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</tt>
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</pre>
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</li>
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<li>
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<p>Set up <a href="../utilities/nohup.html"><i>nohup</i></a> so that it can deal with an argument that is itself an alias name:</p>
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<pre>
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<tt>alias nohup="nohup "
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</tt>
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</pre>
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</li>
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</ol>
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</blockquote>
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<h4><a name="tag_04_02_18"></a>RATIONALE</h4>
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<blockquote>
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<p>The <i>alias</i> description is based on historical KornShell implementations. Known differences exist between that and the C
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shell. The KornShell version was adopted to be consistent with all the other KornShell features in this volume of
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IEEE Std 1003.1-2001, such as command line editing.</p>
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<p>Since <i>alias</i> affects the current shell execution environment, it is generally provided as a shell regular built-in.</p>
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<p>Historical versions of the KornShell have allowed aliases to be exported to scripts that are invoked by the same shell. This is
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triggered by the <i>alias</i> <b>-x</b> flag; it is allowed by this volume of IEEE Std 1003.1-2001 only when an explicit
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extension such as <b>-x</b> is used. The standard developers considered that aliases were of use primarily to interactive users and
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that they should normally not affect shell scripts called by those users; functions are available to such scripts.</p>
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<p>Historical versions of the KornShell had not written aliases in a quoted manner suitable for reentry to the shell, but this
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volume of IEEE Std 1003.1-2001 has made this a requirement for all similar output. Therefore, consistency with this
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volume of IEEE Std 1003.1-2001 was chosen over this detail of historical practice.</p>
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</blockquote>
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<h4><a name="tag_04_02_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_02_20"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="xcu_chap02.html#tag_02_09_05"><i>Function Definition Command</i></a></p>
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</blockquote>
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<h4><a name="tag_04_02_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_02_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 APPLICATION USAGE section is added.</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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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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"../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>
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