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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>eval</title></head><body bgcolor="white"><basefont size="3"> <a name="eval"></a> <a name="tag_04_44"></a><!-- eval --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_04_44_01"></a>NAME</h4><blockquote>eval - construct command by concatenating arguments</blockquote><h4><a name="tag_04_44_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>eval</tt> <b>[</b><i>argument</i> <tt>...</tt><b>]</b></code></p></blockquote><h4><a name="tag_04_44_03"></a>DESCRIPTION</h4><blockquote><p>The <i>eval</i> utility shall construct a command by concatenating <i>argument</i>s together, separating each with a<space>. The constructed command shall be read and executed by the shell.</p></blockquote><h4><a name="tag_04_44_04"></a>OPTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_44_05"></a>OPERANDS</h4><blockquote><p>See the DESCRIPTION.</p></blockquote><h4><a name="tag_04_44_06"></a>STDIN</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_44_07"></a>INPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_44_08"></a>ENVIRONMENT VARIABLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_44_09"></a>ASYNCHRONOUS EVENTS</h4><blockquote><p>Default.</p></blockquote><h4><a name="tag_04_44_10"></a>STDOUT</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_44_11"></a>STDERR</h4><blockquote><p>The standard error shall be used only for diagnostic messages.</p></blockquote><h4><a name="tag_04_44_12"></a>OUTPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_44_13"></a>EXTENDED DESCRIPTION</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_44_14"></a>EXIT STATUS</h4><blockquote><p>If there are no <i>argument</i>s, or only null arguments, <i>eval</i> shall return a zero exit status; otherwise, it shallreturn the exit status of the command defined by the string of concatenated <i>argument</i>s separated by <space>s.</p></blockquote><h4><a name="tag_04_44_15"></a>CONSEQUENCES OF ERRORS</h4><blockquote><p>Default.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_04_44_16"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_44_17"></a>EXAMPLES</h4><blockquote><pre><tt>foo=10 x=fooy='$'$xecho $y</tt><b>$foo</b><tt>eval y='$'$xecho $y</tt><b>10</b></pre></blockquote><h4><a name="tag_04_44_18"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_44_19"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_44_20"></a>SEE ALSO</h4><blockquote><p><a href="xcu_chap02.html#tag_02_14"><i>Special Built-In Utilities</i></a></p></blockquote><h4><a name="tag_04_44_21"></a>CHANGE HISTORY</h4><h4><a name="tag_04_44_22"></a>Issue 6</h4><blockquote><p>IEEE Std 1003.1-2001/Cor 1-2002, item XCU/TC1/D6/5 is applied so that the reference page sections use terms asdescribed in the Utility Description Defaults ( <a href="xcu_chap01.html#tag_01_11"><i>Utility Description Defaults</i></a> ). Nochange in behavior is intended.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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