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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) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>export</title></head><body bgcolor="white"><basefont size="3"> <a name="export"></a> <a name="tag_04_49"></a><!-- export --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_04_49_01"></a>NAME</h4><blockquote>export - set the export attribute for variables</blockquote><h4><a name="tag_04_49_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>export name</tt><b>[</b><tt>=</tt><i>word</i><b>]</b><tt>...<br><br> export -p<br></tt></code></p></blockquote><h4><a name="tag_04_49_03"></a>DESCRIPTION</h4><blockquote><p>The shell shall give the <i>export</i> attribute to the variables corresponding to the specified <i>name</i>s, which shall causethem to be in the environment of subsequently executed commands. If the name of a variable is followed by = <i>word</i>, then thevalue of that variable shall be set to <i>word</i>.</p><p>The <i>export</i> special built-in shall support the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap12.html#tag_12_02">Section 12.2, Utility Syntax Guidelines</a>.</p><p>When <b>-p</b> is specified, <i>export</i> shall write to the standard output the names and values of all exported variables, inthe following format:</p><pre><tt>"export %s=%s\n", <</tt><i>name</i><tt>>, <</tt><i>value</i><tt>></tt></pre><p>if <i>name</i> is set, and:</p><pre><tt>"export %s\n", <</tt><i>name</i><tt>></tt></pre><p>if <i>name</i> is unset.</p><p>The shell shall format the output, including the proper use of quoting, so that it is suitable for reinput to the shell ascommands that achieve the same exporting results, except:</p><ol><li><p>Read-only variables with values cannot be reset.</p></li><li><p>Variables that were unset at the time they were output need not be reset to the unset state if a value is assigned to thevariable between the time the state was saved and the time at which the saved output is reinput to the shell.</p></li></ol><p>When no arguments are given, the results are unspecified.</p></blockquote><h4><a name="tag_04_49_04"></a>OPTIONS</h4><blockquote><p>See the DESCRIPTION.</p></blockquote><h4><a name="tag_04_49_05"></a>OPERANDS</h4><blockquote><p>See the DESCRIPTION.</p></blockquote><h4><a name="tag_04_49_06"></a>STDIN</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_49_07"></a>INPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_49_08"></a>ENVIRONMENT VARIABLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_49_09"></a>ASYNCHRONOUS EVENTS</h4><blockquote><p>Default.</p></blockquote><h4><a name="tag_04_49_10"></a>STDOUT</h4><blockquote><p>See the DESCRIPTION.</p></blockquote><h4><a name="tag_04_49_11"></a>STDERR</h4><blockquote><p>The standard error shall be used only for diagnostic messages.</p></blockquote><h4><a name="tag_04_49_12"></a>OUTPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_49_13"></a>EXTENDED DESCRIPTION</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_49_14"></a>EXIT STATUS</h4><blockquote><p>Zero.</p></blockquote><h4><a name="tag_04_49_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_49_16"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_49_17"></a>EXAMPLES</h4><blockquote><p>Export <i>PWD</i> and <i>HOME</i> variables:</p><pre><tt>export PWD HOME</tt></pre><p>Set and export the <i>PATH</i> variable:</p><pre><tt>export PATH=/local/bin:$PATH</tt></pre><p>Save and restore all exported variables:</p><pre><tt>export -p ></tt> <i>temp-file</i><tt>unset</tt> <i>a lot of variables</i><tt>...</tt> <i>processing</i><tt>.</tt> <i>temp-file</i></pre></blockquote><h4><a name="tag_04_49_18"></a>RATIONALE</h4><blockquote><p>Some historical shells use the no-argument case as the functional equivalent of what is required here with <b>-p</b>. Thisfeature was left unspecified because it is not historical practice in all shells, and some scripts may rely on the now-unspecifiedresults on their implementations. Attempts to specify the <b>-p</b> output as the default case were unsuccessful in achievingconsensus. The <b>-p</b> option was added to allow portable access to the values that can be saved and then later restored using;for example, a <a href="../utilities/dot.html"><i>dot</i></a> script.</p></blockquote><h4><a name="tag_04_49_19"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_49_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_49_21"></a>CHANGE HISTORY</h4><h4><a name="tag_04_49_22"></a>Issue 6</h4><blockquote><p>IEEE PASC Interpretation 1003.2 #203 is applied, clarifying the format when a variable is unset.</p><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><p>IEEE Std 1003.1-2001/Cor 1-2002, item XCU/TC1/D6/6 is applied, adding the following text to the end of the firstparagraph of the DESCRIPTION: ``If the name of a variable is followed by = <i>word</i>, then the value of that variable shall beset to <i>word</i>.''. The reason for this change is that the SYNOPSIS for <i>export</i> includes:</p><pre><tt>export name</tt><b>[</b><tt>=</tt><i>word</i><b>]</b><tt>...</tt></pre><p>but the meaning of the optional ``= <i>word</i>'' is never explained in the text.</p></blockquote><div class="box"><em>End of informative text.</em></div><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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