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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>pathchk</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_001_014_1669"> </a>NAME</h4><blockquote>pathchk - check pathnames</blockquote><h4><a name = "tag_001_014_1670"> </a>SYNOPSIS</h4><blockquote><pre><code>pathchk <b>[</b>-p<b>] </b><i>pathname</i>...</code></pre></blockquote><h4><a name = "tag_001_014_1671"> </a>DESCRIPTION</h4><blockquote>The<i>pathchk</i>utility will check that one or more pathnames are valid(that is, they could be used to access or create a file without causing syntaxerrors) and portable (that is, no filename truncation will result).More extensive portability checks are provided by the<b>-p</b>option.<p>By default, the<i>pathchk</i>utility will check each component of each<i>pathname</i>operand based on the underlying file system.A diagnostic will be written for each<i>pathname</i>operand that:<ul><p><li>is longer than{PATH_MAX}bytes (see<b>Pathname Variable Values</b>in the <b>XSH</b> specification<i><a href="../xsh/limits.h.html"><limits.h></a></i>description)<p><li>contains any component longer than{NAME_MAX}bytes in its containing directory<p><li>contains any component in a directory that is not searchable<p><li>contains any character in any component that is not valid in itscontaining directory.<p></ul><p>The format of the diagnostic message is not specified, but will indicatethe error detected and the corresponding<i>pathname</i>operand.<p>It will not be considered an error if one or more components of a<i>pathname</i>operand do not exist as long as a file matching the pathname specifiedby the missing components could be created that does not violate anyof the checks specified above.</blockquote><h4><a name = "tag_001_014_1672"> </a>OPTIONS</h4><blockquote>The<i>pathchk</i>utility supports the <b>XBD</b> specification, <a href="../xbd/utilconv.html#usg"><b>Utility Syntax Guidelines</b> </a> .<p>The following option is supported:<dl compact><dt><b>-p</b><dd>Instead of performing checks based on the underlying file system,write a diagnostic for each<i>pathname</i>operand that:<ul><li>is longer than{_POSIX_PATH_MAX}bytes (see<b>Minimum Values</b>in the <b>XSH</b> specification<i><a href="../xsh/limits.h.html"><limits.h></a></i>description)<li>contains any component longer than{_POSIX_NAME_MAX}bytes<li>contains any character in any component that is notin the portable filename character set.</ul></dl></blockquote><h4><a name = "tag_001_014_1673"> </a>OPERANDS</h4><blockquote>The following operand is supported:<dl compact><dt><i>pathname</i><dd>A pathname to be checked.</dl></blockquote><h4><a name = "tag_001_014_1674"> </a>STDIN</h4><blockquote>Not used.</blockquote><h4><a name = "tag_001_014_1675"> </a>INPUT FILES</h4><blockquote>None.<br></blockquote><h4><a name = "tag_001_014_1676"> </a>ENVIRONMENT VARIABLES</h4><blockquote>The following environment variables affect the execution of<i>pathchk</i>:<dl compact><dt><i>LANG</i><dd>Provide a default value for the internationalisation variablesthat are unset or null.If<i>LANG</i>is unset or null, the corresponding value from theimplementation-dependent default locale will be used.If any of the internationalisation variables contains an invalid setting, theutility will behave as if none of the variables had been defined.<dt><i>LC_ALL</i><dd>If set to a non-empty string value,override the values of all the other internationalisation variables.<dt><i>LC_CTYPE</i><dd>Determine thelocale for the interpretation of sequences of bytes of text data ascharacters (for example, single- as opposed to multi-byte charactersin arguments).<dt><i>LC_MESSAGES</i><dd>Determine the locale that should be used to affectthe format and contents of diagnosticmessages written to standard error.<dt><i>NLSPATH</i><dd>Determine the location of message cataloguesfor the processing of<i>LC_MESSAGES .</i></dl></blockquote><h4><a name = "tag_001_014_1677"> </a>ASYNCHRONOUS EVENTS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_1678"> </a>STDOUT</h4><blockquote>Not used.</blockquote><h4><a name = "tag_001_014_1679"> </a>STDERR</h4><blockquote>Used only for diagnostic messages.</blockquote><h4><a name = "tag_001_014_1680"> </a>OUTPUT FILES</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_1681"> </a>EXTENDED DESCRIPTION</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_1682"> </a>EXIT STATUS</h4><blockquote>The following exit values are returned:<dl compact><dt>0<dd>All<i>pathname</i>operands passed all of the checks.<dt>>0<dd>An error occurred.</dl></blockquote><h4><a name = "tag_001_014_1683"> </a>CONSEQUENCES OF ERRORS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_1684"> </a>APPLICATION USAGE</h4><blockquote>The<i><a href="test.html">test</a></i>utilitycan be used to determine if a given pathnamenames an existing file; it will not, however, give any indication ofwhether or not any component of the pathname was truncated in a directorywhere the{_POSIX_NO_TRUNC}feature is not in effect.The<i>pathchk</i>utility does not check for fileexistence; it performs checks to determine if a pathname does exist orcould be created with no pathname component truncation.<p>The<i>noclobber</i>option in the shell (see the<i>set</i>special built-in)can be used to atomically create a file.As with all file creation semantics inthe <b>XSH</b> specification, it guarantees atomic creation, but still depends on applicationsto agree on conventions and cooperate on the use of files afterthey have been created.<br></blockquote><h4><a name = "tag_001_014_1685"> </a>EXAMPLES</h4><blockquote>To verify that all pathnames in an imported data interchange archive arelegitimate and unambiguous on the current system:<pre><code>pax -f archive | sed -e '/ == .*/s///' | xargs pathchkif [ $? -eq 0 ]then pax -r -f archiveelse echo Investigate problems before importing files. exit 1fi</code></pre><p>To verify that all files in the current directory hierarchy could bemoved to any system conforming to the <b>XSH</b> specification that also supports the<i><a href="pax.html">pax</a></i>utility:<pre><code>find . -print | xargs pathchk -pif [ $? -eq 0 ]then pax -w -f archive .else echo Portable archive cannot be created. exit 1fi</code></pre><p>To verify that a user-supplied pathname names a readable file and thatthe application can create a file extending the given path without truncationand without overwriting any existing file:<pre><code>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"</code></pre><p>The following assumptions are made in this example:<ol><p><li><b>PROCESSING</b>represents the code that will be used by theapplication to use<b>$path</b>once it is verified that<b>$path.out</b>will work as intended.<p><li>The state of the<i>noclobber</i>option is unknown when this codeis 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.)<br><p><li>Note the usage of:<pre><code>rm "$path.out" > "$path.out"</code></pre><ol type = a><p><li>The<i>pathchk</i>command has already verified, at this point, that<b>$path.out</b>will not be truncated.<p><li>With the<i>noclobber</i>option set, the shell will verify that<b>$path.out</b>does not already exist before invoking<i><a href="rm.html">rm</a></i>.<p><li>If the shell succeeded in creating<b>$path.out</b>,<i><a href="rm.html">rm</a></i>will remove it so that the application can create the file again in the<b>PROCESSING</b>step.<p><li>If the<b>PROCESSING</b>step wants the file to exist already when it is invoked, the:<pre><code>rm "$path.out" > "$path.out"</code></pre>should be replaced with:<pre><code>> "$path.out"</code></pre>which will verify that the file did not already exist, but leave<b>$path.out</b>in place for use by<b>PROCESSING</b>.<p></ol><p></ol></blockquote><h4><a name = "tag_001_014_1686"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_1687"> </a>SEE ALSO</h4><blockquote><i><a href="test.html">test</a></i>,<xref href=redir><a href="chap2.html#tag_001_007">Redirection</a></xref>.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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