245 lines
6.9 KiB
HTML
245 lines
6.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<meta name="generator" content="HTML Tidy, see www.w3.org">
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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>dirname</title>
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</head>
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<body bgcolor="white">
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<script type="text/javascript" language="JavaScript" src="../jscript/codes.js">
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<basefont size="3"> <a name="dirname"></a> <a name="tag_03_107"></a><!-- dirname -->
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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_03_107_01"></a>NAME</h4>
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<blockquote>dirname - report the parent directory name of a file pathname</blockquote>
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<h4><a name="tag_03_107_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/libgen.h.html">libgen.h</a>><br>
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<br>
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char *dirname(char *</tt><i>path</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_107_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>dirname</i>() function shall take a pointer to a character string that contains a pathname, and return a pointer to a
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string that is a pathname of the parent directory of that file. Trailing <tt>'/'</tt> characters in the path are not counted as
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part of the path.</p>
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<p>If <i>path</i> does not contain a <tt>'/'</tt> , then <i>dirname</i>() shall return a pointer to the string <tt>"."</tt> . If
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<i>path</i> is a null pointer or points to an empty string, <i>dirname</i>() shall return a pointer to the string <tt>"."</tt>
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.</p>
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<p>The <i>dirname</i>() function need not be reentrant. A function that is not required to be reentrant is not required to be
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thread-safe.</p>
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</blockquote>
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<h4><a name="tag_03_107_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>The <i>dirname</i>() function shall return a pointer to a string that is the parent directory of <i>path</i>. If <i>path</i> is
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a null pointer or points to an empty string, a pointer to a string <tt>"."</tt> is returned.</p>
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<p>The <i>dirname</i>() function may modify the string pointed to by <i>path</i>, and may return a pointer to static storage that
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may then be overwritten by subsequent calls to <i>dirname</i>().</p>
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</blockquote>
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<h4><a name="tag_03_107_05"></a>ERRORS</h4>
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<blockquote>
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<p>No errors are defined.</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_03_107_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>The following code fragment reads a pathname, changes the current working directory to the parent directory, and opens the
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file.</p>
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<pre>
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<tt>char path[PATH_MAX], *pathcopy;
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int fd;
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fgets(path, PATH_MAX, stdin);
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pathcopy = strdup(path);
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chdir(dirname(pathcopy));
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fd = open(basename(path), O_RDONLY);
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</tt>
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</pre>
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<h5><a name="tag_03_107_06_01"></a>Sample Input and Output Strings for dirname()</h5>
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<p>In the following table, the input string is the value pointed to by <i>path</i>, and the output string is the return value of
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the <i>dirname</i>() function.</p>
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<center>
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<table border="1" cellpadding="3" align="center">
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<tr valign="top">
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<th align="center">
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<p class="tent"><b>Input String</b></p>
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</th>
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<th align="center">
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<p class="tent"><b>Output String</b></p>
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</th>
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</tr>
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<tr valign="top">
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<td align="left">
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<p class="tent">"/usr/lib"</p>
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</td>
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<td align="left">
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<p class="tent">"/usr"</p>
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</td>
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</tr>
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<tr valign="top">
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<td align="left">
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<p class="tent">"/usr/"</p>
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</td>
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<td align="left">
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<p class="tent">"/"</p>
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</td>
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</tr>
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<tr valign="top">
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<td align="left">
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<p class="tent">"usr"</p>
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</td>
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<td align="left">
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<p class="tent">"."</p>
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</td>
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</tr>
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<tr valign="top">
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<td align="left">
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<p class="tent">"/"</p>
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</td>
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<td align="left">
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<p class="tent">"/"</p>
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</td>
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</tr>
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<tr valign="top">
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<td align="left">
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<p class="tent">"."</p>
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</td>
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<td align="left">
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<p class="tent">"."</p>
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</td>
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</tr>
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<tr valign="top">
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<td align="left">
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<p class="tent">".."</p>
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</td>
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<td align="left">
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<p class="tent">"."</p>
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</td>
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</tr>
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</table>
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</center>
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<h5><a name="tag_03_107_06_02"></a>Changing the Current Directory to the Parent Directory</h5>
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<p>The following program fragment reads a pathname, changes the current working directory to the parent directory, and opens the
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file.</p>
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<pre>
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<tt>#include <unistd.h>
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#include <limits.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <string.h>
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#include <libgen.h>
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...
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char path[PATH_MAX], *pathcopy;
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int fd;
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...
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fgets(path, PATH_MAX, stdin);
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pathcopy = strdup(path);
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chdir(dirname(pathcopy));
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fd = open(basename(path), O_RDONLY);
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</tt>
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</pre>
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</blockquote>
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<h4><a name="tag_03_107_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>The <i>dirname</i>() and <a href="../functions/basename.html"><i>basename</i>()</a> functions together yield a complete
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pathname. The expression <i>dirname</i>(<i>path</i>) obtains the pathname of the directory where <i>basename</i>(<i>path</i>) is
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found.</p>
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<p>Since the meaning of the leading <tt>"//"</tt> is implementation-defined, <i>dirname</i>(" <b>//foo</b>) may return either
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<tt>"//"</tt> or <tt>'/'</tt> (but nothing else).</p>
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</blockquote>
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<h4><a name="tag_03_107_08"></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_03_107_09"></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_03_107_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="basename.html"><i>basename</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/libgen.h.html"><i><libgen.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_107_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 4, Version 2.</p>
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</blockquote>
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<h4><a name="tag_03_107_12"></a>Issue 5</h4>
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<blockquote>
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<p>Moved from X/OPEN UNIX extension to BASE.</p>
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<p>Normative text previously in the APPLICATION USAGE section is moved to the DESCRIPTION.</p>
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<p>A note indicating that this function need not be reentrant is added to the DESCRIPTION.</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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<hr size="2" noshade>
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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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]</font></center>
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