📄 break.html
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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>break</title></head><body bgcolor="white"><basefont size="3"> <a name="break"></a> <a name="tag_04_11"></a><!-- break --> <!--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_11_01"></a>NAME</h4><blockquote>break - exit from for, while, or until loop</blockquote><h4><a name="tag_04_11_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>break</tt> <b>[</b><i>n</i><b>]</b></code></p></blockquote><h4><a name="tag_04_11_03"></a>DESCRIPTION</h4><blockquote><p>The <i>break</i> utility shall exit from the smallest enclosing <b>for</b>, <b>while</b>, or <b>until</b> loop, if any; or fromthe <i>n</i>th enclosing loop if <i>n</i> is specified. The value of <i>n</i> is an unsigned decimal integer greater than or equalto 1. The default shall be equivalent to <i>n</i>=1. If <i>n</i> is greater than the number of enclosing loops, the outermostenclosing loop shall be exited. Execution shall continue with the command immediately following the loop.</p></blockquote><h4><a name="tag_04_11_04"></a>OPTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_11_05"></a>OPERANDS</h4><blockquote><p>See the DESCRIPTION.</p></blockquote><h4><a name="tag_04_11_06"></a>STDIN</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_11_07"></a>INPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_11_08"></a>ENVIRONMENT VARIABLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_11_09"></a>ASYNCHRONOUS EVENTS</h4><blockquote><p>Default.</p></blockquote><h4><a name="tag_04_11_10"></a>STDOUT</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_11_11"></a>STDERR</h4><blockquote><p>The standard error shall be used only for diagnostic messages.</p></blockquote><h4><a name="tag_04_11_12"></a>OUTPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_11_13"></a>EXTENDED DESCRIPTION</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_11_14"></a>EXIT STATUS</h4><blockquote><dl compact><dt> 0</dt><dd>Successful completion.</dd><dt>>0</dt><dd>The <i>n</i> value was not an unsigned decimal integer greater than or equal to 1.</dd></dl></blockquote><h4><a name="tag_04_11_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_11_16"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_11_17"></a>EXAMPLES</h4><blockquote><pre><tt>for i in * do if test -d "$i" then break fi done</tt></pre></blockquote><h4><a name="tag_04_11_18"></a>RATIONALE</h4><blockquote><p>In early proposals, consideration was given to expanding the syntax of <i>break</i> and <a href="../utilities/continue.html"><i>continue</i></a> to refer to a label associated with the appropriate loop as a preferablealternative to the <i>n</i> method. However, this volume of IEEE Std 1003.1-2001 does reserve the name space of commandnames ending with a colon. It is anticipated that a future implementation could take advantage of this and provide somethinglike:</p><pre><tt>outofloop: for i in a b c d edo for j in 0 1 2 3 4 5 6 7 8 9 do if test -r "${i}${j}" then break outofloop fi donedone</tt></pre><p>and that this might be standardized after implementation experience is achieved.</p></blockquote><h4><a name="tag_04_11_19"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_11_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_11_21"></a>CHANGE HISTORY</h4><h4><a name="tag_04_11_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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