182 lines
3.9 KiB
HTML
182 lines
3.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<meta name="generator" content="HTML Tidy, see www.w3.org">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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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>colon</title>
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</head>
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<body bgcolor="white">
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<basefont size="3"> <a name="colon"></a> <a name="tag_04_22"></a><!-- colon -->
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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_22_01"></a>NAME</h4>
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<blockquote>colon - null utility</blockquote>
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<h4><a name="tag_04_22_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>:</tt> <b>[</b><i>argument</i> <tt>...</tt><b>]</b></code></p>
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</blockquote>
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<h4><a name="tag_04_22_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>This utility shall only expand command <i>argument</i>s. It is used when a command is needed, as in the <b>then</b> condition of
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an <b>if</b> command, but nothing is to be done by the command.</p>
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</blockquote>
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<h4><a name="tag_04_22_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_22_05"></a>OPERANDS</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_22_06"></a>STDIN</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_22_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_22_08"></a>ENVIRONMENT VARIABLES</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_22_09"></a>ASYNCHRONOUS EVENTS</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_22_10"></a>STDOUT</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_22_11"></a>STDERR</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_22_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_22_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_22_14"></a>EXIT STATUS</h4>
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<blockquote>
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<p>Zero.</p>
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</blockquote>
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<h4><a name="tag_04_22_15"></a>CONSEQUENCES OF ERRORS</h4>
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<blockquote>
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<p>None.</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_22_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_22_17"></a>EXAMPLES</h4>
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<blockquote>
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<pre>
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<tt>: ${X=abc}
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if false
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then :
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else echo $X
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fi
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</tt><b>abc</b>
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</pre>
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<p>As with any of the special built-ins, the null utility can also have variable assignments and redirections associated with it,
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such as:</p>
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<pre>
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<tt>x=y : > z
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</tt>
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</pre>
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<p>which sets variable <i>x</i> to the value <i>y</i> (so that it persists after the null utility completes) and creates or
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truncates file <b>z</b>.</p>
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</blockquote>
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<h4><a name="tag_04_22_18"></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_04_22_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_22_20"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="xcu_chap02.html#tag_02_14"><i>Special Built-In Utilities</i></a></p>
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</blockquote>
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<h4><a name="tag_04_22_21"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>None.</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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<center><font size="2"><!--footer start-->
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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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[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href=
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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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