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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>cd</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="cd"></a> <a name="tag_04_15"></a><!-- cd --> <!--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_15_01"></a>NAME</h4><blockquote>cd - change the working directory</blockquote><h4><a name="tag_04_15_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>cd</tt> <b>[</b><tt>-L | -P</tt><b>] [</b><i>directory</i><b>]</b><tt><br><br>cd -<br></tt></code></p></blockquote><h4><a name="tag_04_15_03"></a>DESCRIPTION</h4><blockquote><p>The <i>cd</i> utility shall change the working directory of the current shell execution environment (see <a href="xcu_chap02.html#tag_02_12"><i>Shell Execution Environment</i></a> ) by executing the following steps in sequence. (In thefollowing steps, the symbol <b>curpath</b> represents an intermediate value used to simplify the description of the algorithm usedby <i>cd</i>. There is no requirement that <b>curpath</b> be made visible to the application.)</p><ol><li><p>If no <i>directory</i> operand is given and the <i>HOME</i> environment variable is empty or undefined, the default behavior isimplementation-defined and no further steps shall be taken.</p></li><li><p>If no <i>directory</i> operand is given and the <i>HOME</i> environment variable is set to a non-empty value, the <i>cd</i>utility shall behave as if the directory named in the <i>HOME</i> environment variable was specified as the <i>directory</i>operand.</p></li><li><p>If the <i>directory</i> operand begins with a slash character, set <b>curpath</b> to the operand and proceed to step 7.</p></li><li><p>If the first component of the <i>directory</i> operand is dot or dot-dot, proceed to step 6.</p></li><li><p>Starting with the first pathname in the colon-separated pathnames of <i>CDPATH</i> (see the ENVIRONMENT VARIABLES section) ifthe pathname is non-null, test if the concatenation of that pathname, a slash character, and the <i>directory</i> operand names adirectory. If the pathname is null, test if the concatenation of dot, a slash character, and the operand names a directory. Ineither case, if the resulting string names an existing directory, set <b>curpath</b> to that string and proceed to step 7.Otherwise, repeat this step with the next pathname in <i>CDPATH</i> until all pathnames have been tested.</p></li><li><p>Set <b>curpath</b> to the string formed by the concatenation of the value of <i>PWD ,</i> a slash character, and theoperand.</p></li><li><p>If the <b>-P</b> option is in effect, the <i>cd</i> utility shall perform actions equivalent to the <a href="../functions/chdir.html"><i>chdir</i>()</a> function, called with <b>curpath</b> as the <i>path</i> argument. If these actionssucceed, the <i>PWD</i> environment variable shall be set to an absolute pathname for the current working directory and shall notcontain filename components that, in the context of pathname resolution, refer to a file of type symbolic link. If there isinsufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, thevalue of the <i>PWD</i> environment variable is unspecified. If the actions equivalent to <a href="../functions/chdir.html"><i>chdir</i>()</a> fail for any reason, the <i>cd</i> utility shall display an appropriate error messageand not alter the <i>PWD</i> environment variable. Whether the actions equivalent to <a href="../functions/chdir.html"><i>chdir</i>()</a> succeed or fail, no further steps shall be taken.</p></li><li><p>The <b>curpath</b> value shall then be converted to canonical form as follows, considering each component from beginning to end,in sequence:</p><ol type="a"><li><p>Dot components and any slashes that separate them from the next component shall be deleted.</p></li><li><p>For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, the preceding component, allslashes separating the preceding component from dot-dot, dot-dot and all slashes separating dot-dot from the following componentshall be deleted.</p></li><li><p>An implementation may further simplify <b>curpath</b> by removing any trailing slash characters that are not also leadingslashes, replacing multiple non-leading consecutive slashes with a single slash, and replacing three or more leading slashes with asingle slash. If, as a result of this canonicalization, the <b>curpath</b> variable is null, no further steps shall be taken.</p></li></ol></li><li><p>The <i>cd</i> utility shall then perform actions equivalent to the <a href="../functions/chdir.html"><i>chdir</i>()</a> functioncalled with <b>curpath</b> as the <i>path</i> argument. If these actions failed for any reason, the <i>cd</i> utility shall displayan appropriate error message and no further steps shall be taken. The <i>PWD</i> environment variable shall be set to<b>curpath</b>.</p></li></ol><p>If, during the execution of the above steps, the <i>PWD</i> environment variable is changed, the <i>OLDPWD</i> environmentvariable shall also be changed to the value of the old working directory (that is the current working directory immediately priorto the call to <i>cd</i>).</p></blockquote><h4><a name="tag_04_15_04"></a>OPTIONS</h4><blockquote><p>The <i>cd</i> utility shall conform to 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>The following options shall be supported by the implementation:</p><dl compact><dt><b>-L</b></dt><dd>Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed(see steps 8. and 9. in the DESCRIPTION).</dd><dt><b>-P</b></dt><dd>Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (seestep 7. in the DESCRIPTION).</dd></dl><p>If both <b>-L</b> and <b>-P</b> options are specified, the last of these options shall be used and all others ignored. Ifneither <b>-L</b> nor <b>-P</b> is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION.</p></blockquote><h4><a name="tag_04_15_05"></a>OPERANDS</h4><blockquote><p>The following operands shall be supported:</p><dl compact><dt><i>directory</i></dt><dd>An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relativepathname by <i>cd</i> depends on the <b>-L</b> option and the <i>CDPATH</i> and <i>PWD</i> environment variables. If<i>directory</i> is an empty string, the results are unspecified.</dd><dt>-</dt><dd>When a hyphen is used as the operand, this shall be equivalent to the command: <pre><tt>cd "$OLDPWD" && pwd</tt></pre><p>which changes to the previous working directory and then writes its name.</p></dd></dl></blockquote><h4><a name="tag_04_15_06"></a>STDIN</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_15_07"></a>INPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_15_08"></a>ENVIRONMENT VARIABLES</h4><blockquote><p>The following environment variables shall affect the execution of <i>cd</i>:</p><dl compact><dt><i>CDPATH</i></dt><dd>A colon-separated list of pathnames that refer to directories. The <i>cd</i> utility shall use this list in its attempt tochange the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the currentdirectory. If <i>CDPATH</i> is not set, it shall be treated as if it were an empty string.</dd><dt><i>HOME</i></dt><dd>The name of the directory, used when no <i>directory</i> operand is specified.</dd><dt><i>LANG</i></dt><dd>Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html#tag_08_02">Section 8.2, Internationalization Variables</a> forthe precedence of internationalization variables used to determine the values of locale categories.)</dd><dt><i>LC_ALL</i></dt><dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd><dt><i>LC_CTYPE</i></dt><dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte asopposed to multi-byte characters in arguments).</dd><dt><i>LC_MESSAGES</i></dt><dd>Determine the locale that should be used to affect the format and contents of diagnostic messages written to standarderror.</dd><dt><i>NLSPATH</i></dt><dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Determine the location of message catalogs for the processing of <i>LC_MESSAGES .</i> <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd><dt><i>OLDPWD</i></dt><dd>A pathname of the previous working directory, used by <i>cd</i> <b>-</b>.</dd><dt><i>PWD</i></dt><dd>This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of <i>PWD ,</i> thebehavior of <i>cd</i> is unspecified.</dd></dl></blockquote><h4><a name="tag_04_15_09"></a>ASYNCHRONOUS EVENTS</h4><blockquote><p>Default.</p></blockquote><h4><a name="tag_04_15_10"></a>STDOUT</h4><blockquote><p>If a non-empty directory name from <i>CDPATH</i> is used, or if <i>cd</i> <b>-</b> is used, an absolute pathname of the newworking directory shall be written to the standard output as follows:</p><pre><tt>"%s\n", <</tt><i>new directory</i><tt>></tt></pre><p>Otherwise, there shall be no output.</p></blockquote><h4><a name="tag_04_15_11"></a>STDERR</h4><blockquote><p>The standard error shall be used only for diagnostic messages.</p></blockquote><h4><a name="tag_04_15_12"></a>OUTPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_15_13"></a>EXTENDED DESCRIPTION</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_15_14"></a>EXIT STATUS</h4><blockquote><p>The following exit values shall be returned:</p><dl compact><dt> 0</dt><dd>The directory was successfully changed.</dd><dt>>0</dt><dd>An error occurred.</dd></dl></blockquote><h4><a name="tag_04_15_15"></a>CONSEQUENCES OF ERRORS</h4><blockquote><p>The working directory shall remain unchanged.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_04_15_16"></a>APPLICATION USAGE</h4><blockquote><p>Since <i>cd</i> affects the current shell execution environment, it is always provided as a shell regular built-in. If it iscalled in a subshell or separate utility execution environment, such as one of the following:</p><pre><tt>(cd /tmp)nohup cdfind . -exec cd {} \;</tt></pre><p>it does not affect the working directory of the caller's environment.</p><p>The user must have execute (search) permission in <i>directory</i> in order to change to it.</p></blockquote><h4><a name="tag_04_15_17"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_15_18"></a>RATIONALE</h4><blockquote><p>The use of the <i>CDPATH</i> was introduced in the System V shell. Its use is analogous to the use of the <i>PATH</i> variablein the shell. The BSD C shell used a shell parameter <i>cdpath</i> for this purpose.</p><p>A common extension when <i>HOME</i> is undefined is to get the login directory from the user database for the invoking user.This does not occur on System V implementations.</p><p>Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component,selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the<tt>'/'</tt> in the pathname, remembering what the user typed, rather than performing the equivalent of:</p><pre><tt>chdir("..");</tt></pre><p>In such a shell, the following commands would not necessarily produce equivalent output for all directories:</p><pre><tt>cd .. && ls ls ..</tt></pre><p>This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is,while this behavior has been optionally available in the KornShell, other shells have historically not supported thisfunctionality. The logical pathname is stored in the <i>PWD</i> environment variable when the <i>cd</i> utility completes and thisvalue is used to construct the next directory name if <i>cd</i> is invoked with the <b>-L</b> option.</p></blockquote><h4><a name="tag_04_15_19"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_15_20"></a>SEE ALSO</h4><blockquote><p><a href="xcu_chap02.html#tag_02_12"><i>Shell Execution Environment</i></a>, <a href="pwd.html"><i>pwd</i></a>, the SystemInterfaces volume of IEEE Std 1003.1-2001, <a href="../functions/chdir.html"><i>chdir</i>()</a></p></blockquote><h4><a name="tag_04_15_21"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 2.</p></blockquote><h4><a name="tag_04_15_22"></a>Issue 6</h4><blockquote><p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p><ul><li><p>The <i>cd</i> <b>-</b> operand, <i>PWD ,</i> and <i>OLDPWD</i> are added.</p></li></ul><p>The <b>-L</b> and <b>-P</b> options are added to align with the IEEE P1003.2b draft standard. This also includes theintroduction of a new description to include the effect of these options.<br></p><p>IEEE Std 1003.1-2001/Cor 1-2002, item XCU/TC1/D6/14 is applied, changing the SYNOPSIS to make it clear that the<b>-L</b> and <b>-P</b> options are mutually-exclusive.</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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