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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>pathchk</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="pathchk"></a> <a name="tag_04_99"></a><!-- pathchk --> <!--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_99_01"></a>NAME</h4><blockquote>pathchk - check pathnames</blockquote><h4><a name="tag_04_99_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>pathchk</tt> <b>[</b><tt>-p</tt><b>]</b> <i>pathname</i><tt>...</tt></code></p></blockquote><h4><a name="tag_04_99_03"></a>DESCRIPTION</h4><blockquote><p>The <i>pathchk</i> utility shall check that one or more pathnames are valid (that is, they could be used to access or create afile without causing syntax errors) and portable (that is, no filename truncation results). More extensive portability checks areprovided by the <b>-p</b> option.</p><p>By default, the <i>pathchk</i> utility shall check each component of each <i>pathname</i> operand based on the underlying filesystem. A diagnostic shall be written for each <i>pathname</i> operand that:</p><ul><li><p>Is longer than {PATH_MAX} bytes (see <b>Pathname Variable Values</b> in the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap13.html#tag_13">Chapter 13, Headers</a>, <a href="../basedefs/limits.h.html"><i><limits.h></i></a>)</p></li><li><p>Contains any component longer than {NAME_MAX} bytes in its containing directory</p></li><li><p>Contains any component in a directory that is not searchable</p></li><li><p>Contains any character in any component that is not valid in its containing directory</p></li></ul><p>The format of the diagnostic message is not specified, but shall indicate the error detected and the corresponding<i>pathname</i> operand.</p><p>It shall not be considered an error if one or more components of a <i>pathname</i> operand do not exist as long as a filematching the pathname specified by the missing components could be created that does not violate any of the checks specifiedabove.</p></blockquote><h4><a name="tag_04_99_04"></a>OPTIONS</h4><blockquote><p>The <i>pathchk</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 option shall be supported:</p><dl compact><dt><b>-p</b></dt><dd>Instead of performing checks based on the underlying file system, write a diagnostic for each <i>pathname</i> operand that: <ul><li><p>Is longer than {_POSIX_PATH_MAX} bytes (see <b>Minimum Values</b> in the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap13.html#tag_13">Chapter 13, Headers</a>, <a href="../basedefs/limits.h.html"><i><limits.h></i></a>)</p></li><li><p>Contains any component longer than {_POSIX_NAME_MAX} bytes</p></li><li><p>Contains any character in any component that is not in the portable filename character set</p></li></ul></dd></dl></blockquote><h4><a name="tag_04_99_05"></a>OPERANDS</h4><blockquote><p>The following operand shall be supported:</p><dl compact><dt><i>pathname</i></dt><dd>A pathname to be checked.</dd></dl></blockquote><h4><a name="tag_04_99_06"></a>STDIN</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_99_07"></a>INPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_99_08"></a>ENVIRONMENT VARIABLES</h4><blockquote><p>The following environment variables shall affect the execution of <i>pathchk</i>:</p><dl compact><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></dl></blockquote><h4><a name="tag_04_99_09"></a>ASYNCHRONOUS EVENTS</h4><blockquote><p>Default.</p></blockquote><h4><a name="tag_04_99_10"></a>STDOUT</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_99_11"></a>STDERR</h4><blockquote><p>The standard error shall be used only for diagnostic messages.</p></blockquote><h4><a name="tag_04_99_12"></a>OUTPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_99_13"></a>EXTENDED DESCRIPTION</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_99_14"></a>EXIT STATUS</h4><blockquote><p>The following exit values shall be returned:</p><dl compact><dt> 0</dt><dd>All <i>pathname</i> operands passed all of the checks.</dd><dt>>0</dt><dd>An error occurred.</dd></dl></blockquote><h4><a name="tag_04_99_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_99_16"></a>APPLICATION USAGE</h4><blockquote><p>The <a href="../utilities/test.html"><i>test</i></a> utility can be used to determine whether a given pathname names an existingfile; it does not, however, give any indication of whether or not any component of the pathname was truncated in a directory wherethe _POSIX_NO_TRUNC feature is not in effect. The <i>pathchk</i> utility does not check for file existence; it performs checks todetermine whether a pathname does exist or could be created with no pathname component truncation.</p><p>The <i>noclobber</i> option in the shell (see the <a href="set.html#tag_04_127"><i>set</i></a> special built-in) can be used toatomically create a file. As with all file creation semantics in the System Interfaces volume of IEEE Std 1003.1-2001, itguarantees atomic creation, but still depends on applications to agree on conventions and cooperate on the use of files after theyhave been created.</p></blockquote><h4><a name="tag_04_99_17"></a>EXAMPLES</h4><blockquote><p>To verify that all pathnames in an imported data interchange archive are legitimate and unambiguous on the current system:</p><pre><tt>pax -f archive | sed -e '/ == .*/s///' | xargs pathchkif [ $? -eq 0 ]then pax -r -f archiveelse echo Investigate problems before importing files. exit 1fi</tt></pre><p>To verify that all files in the current directory hierarchy could be moved to any system conforming to the System Interfacesvolume of IEEE Std 1003.1-2001 that also supports the <a href="../utilities/pax.html"><i>pax</i></a> utility:</p><pre><tt>find . -print | xargs pathchk -pif [ $? -eq 0 ]then pax -w -f archive .else echo Portable archive cannot be created. exit 1fi</tt></pre><p>To verify that a user-supplied pathname names a readable file and that the application can create a file extending the givenpath without truncation and without overwriting any existing file:</p><pre><tt>case $- in *C*) reset="";; *) reset="set +C" set -C;;esactest -r "$path" && pathchk "$path.out" && rm "$path.out" > "$path.out"if [ $? -ne 0 ]; then printf "%s: %s not found or %s.out fails \creation checks.\n" $0 "$path" "$path" $reset # Reset the noclobber option in case a trap # on EXIT depends on it. exit 1fi$resetPROCESSING < "$path" > "$path.out"</tt></pre><p>The following assumptions are made in this example:</p><ol><li><p><b>PROCESSING</b> represents the code that is used by the application to use <b>$path</b> once it is verified that<b>$path.out</b> works as intended.</p></li><li><p>The state of the <i>noclobber</i> option is unknown when this code is invoked and should be set on exit to the state it was inwhen this code was invoked. (The <b>reset</b> variable is used in this example to restore the initial state.)</p></li><li><p>Note the usage of:</p><pre><tt>rm "$path.out" > "$path.out"</tt></pre><ol type="a"><li><p>The <i>pathchk</i> command has already verified, at this point, that <b>$path.out</b> is not truncated.</p></li><li><p>With the <i>noclobber</i> option set, the shell verifies that <b>$path.out</b> does not already exist before invoking <a href="../utilities/rm.html"><i>rm</i></a>.</p></li><li><p>If the shell succeeded in creating <b>$path.out</b>, <a href="../utilities/rm.html"><i>rm</i></a> removes it so that theapplication can create the file again in the <b>PROCESSING</b> step.</p></li><li><p>If the <b>PROCESSING</b> step wants the file to exist already when it is invoked, the:</p><pre><tt>rm "$path.out" > "$path.out"</tt></pre><p>should be replaced with:</p><pre><tt>> "$path.out"</tt></pre><p>which verifies that the file did not already exist, but leaves <b>$path.out</b> in place for use by <b>PROCESSING</b>.</p></li></ol></li></ol></blockquote><h4><a name="tag_04_99_18"></a>RATIONALE</h4><blockquote><p>The <i>pathchk</i> utility was new for the ISO POSIX-2:1993 standard. It, along with the <a href="../utilities/set.html"><i>set</i></a> <b>-C</b>( <i>noclobber</i>) option added to the shell, replaces the<i>mktemp</i>, <i>validfnam</i>, and <i>create</i> utilities that appeared in early proposals. All of these utilities were attemptsto solve several common problems:</p><ul><li><p>Verify the validity (for several different definitions of "valid") of a pathname supplied by a user, generated by anapplication, or imported from an external source.</p></li><li><p>Atomically create a file.</p></li><li><p>Perform various string handling functions to generate a temporary filename.</p></li></ul><p>The <i>create</i> utility, included in an early proposal, provided checking and atomic creation in a single invocation of theutility; these are orthogonal issues and need not be grouped into a single utility. Note that the <i>noclobber</i> option alsoprovides a way of creating a lock for process synchronization; since it provides an atomic <i>create</i>, there is no race betweena test for existence and the following creation if it did not exist.</p><p>Having a function like <a href="../functions/tmpnam.html"><i>tmpnam</i>()</a> in the ISO C standard is important in manyhigh-level languages. The shell programming language, however, has built-in string manipulation facilities, making it very easy toconstruct temporary filenames. The names needed obviously depend on the application, but are frequently of a form similar to:</p><pre><b>$TMPDIR/</b><i>application_abbreviation</i><b>$$.</b><i>suffix</i></pre><p>In cases where there is likely to be contention for a given suffix, a simple shell <b>for</b> or <b>while</b> loop can be usedwith the shell <i>noclobber</i> option to create a file without risk of collisions, as long as applications trying to use the samefilename name space are cooperating on the use of files after they have been created.</p></blockquote><h4><a name="tag_04_99_19"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_99_20"></a>SEE ALSO</h4><blockquote><p><a href="xcu_chap02.html#tag_02_07"><i>Redirection</i></a> , <a href="set.html#tag_04_127"><i>set</i></a> , <a href="test.html"><i>test</i></a></p></blockquote><h4><a name="tag_04_99_21"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 4.</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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