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23 <center><font size="2">The Open Group Base Specifications Issue 8<br>
24 IEEE Std 1003.1-2024<br>
25 Copyright © 2001-2024 The IEEE and The Open Group</font></center>
26 <hr size="2" noshade>
27 <a name="top" id="top"></a> <a name="pathchk" id="pathchk"></a> <a name="tag_20_93" id="tag_20_93"></a><!-- pathchk -->
28 <h4 class="mansect"><a name="tag_20_93_01" id="tag_20_93_01"></a>NAME</h4>
29 <blockquote>pathchk — check pathnames</blockquote>
30 <h4 class="mansect"><a name="tag_20_93_02" id="tag_20_93_02"></a>SYNOPSIS</h4>
31 <blockquote class="synopsis">
32 <p><code><tt>pathchk</tt> <b>[</b><tt>-p</tt><b>] [</b><tt>-P</tt><b>]</b> <i>pathname</i><tt>...</tt></code></p>
33 </blockquote>
34 <h4 class="mansect"><a name="tag_20_93_03" id="tag_20_93_03"></a>DESCRIPTION</h4>
35 <blockquote>
36 <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 a
37 file without causing syntax errors) and portable (that is, no filename truncation results). More extensive portability checks are
38 provided by the <b>-p</b> and <b>-P</b> options.</p>
39 <p>By default, the <i>pathchk</i> utility shall check each component of each <i>pathname</i> operand based on the underlying file
40 system. A diagnostic shall be written for each <i>pathname</i> operand that:</p>
41 <ul>
42 <li>
43 <p>Is longer than {PATH_MAX} bytes (see <b>Pathname Variable Values</b> in XBD <a href=
44 "../basedefs/limits.h.html"><i><limits.h></i></a> )</p>
45 </li>
46 <li>
47 <p>Contains any component longer than {NAME_MAX} bytes in its containing directory</p>
48 </li>
49 <li>
50 <p>Contains any component in a directory that is not searchable</p>
51 </li>
52 <li>
53 <p>Contains any byte sequence that is not valid in its containing directory</p>
54 </li>
55 </ul>
56 <p>The format of the diagnostic message is not specified, but shall indicate the error detected and the corresponding
57 <i>pathname</i> operand.</p>
58 <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 file
59 matching the pathname specified by the missing components could be created that does not violate any of the checks specified
60 above.</p>
61 </blockquote>
62 <h4 class="mansect"><a name="tag_20_93_04" id="tag_20_93_04"></a>OPTIONS</h4>
63 <blockquote>
64 <p>The <i>pathchk</i> utility shall conform to XBD <a href="../basedefs/V1_chap12.html#tag_12_02"><i>12.2 Utility Syntax
65 Guidelines</i></a> .</p>
66 <p>The following option shall be supported:</p>
67 <dl compact>
68 <dd></dd>
69 <dt><b>-p</b></dt>
70 <dd>Instead of performing checks based on the underlying file system, write a diagnostic for each <i>pathname</i> operand that:
71 <ul>
72 <li>
73 <p>Is longer than {_POSIX_PATH_MAX} bytes (see <b>Minimum Values</b> in XBD <a href=
74 "../basedefs/limits.h.html"><i><limits.h></i></a> )</p>
75 </li>
76 <li>
77 <p>Contains any component longer than {_POSIX_NAME_MAX} bytes</p>
78 </li>
79 <li>
80 <p>Contains any character in any component that is not in the portable filename character set</p>
81 </li>
82 </ul>
83 </dd>
84 <dt><b>-P</b></dt>
85 <dd>Write a diagnostic for each <i>pathname</i> operand that:
86 <ul>
87 <li>
88 <p>Contains a component whose first character is the <hyphen-minus> character</p>
89 </li>
90 <li>
91 <p>Is empty</p>
92 </li>
93 </ul>
94 </dd>
95 </dl>
96 </blockquote>
97 <h4 class="mansect"><a name="tag_20_93_05" id="tag_20_93_05"></a>OPERANDS</h4>
98 <blockquote>
99 <p>The following operand shall be supported:</p>
100 <dl compact>
101 <dd></dd>
102 <dt><i>pathname</i></dt>
103 <dd>A pathname to be checked.</dd>
104 </dl>
105 </blockquote>
106 <h4 class="mansect"><a name="tag_20_93_06" id="tag_20_93_06"></a>STDIN</h4>
107 <blockquote>
108 <p>Not used.</p>
109 </blockquote>
110 <h4 class="mansect"><a name="tag_20_93_07" id="tag_20_93_07"></a>INPUT FILES</h4>
111 <blockquote>
112 <p>None.</p>
113 </blockquote>
114 <h4 class="mansect"><a name="tag_20_93_08" id="tag_20_93_08"></a>ENVIRONMENT VARIABLES</h4>
115 <blockquote>
116 <p>The following environment variables shall affect the execution of <i>pathchk</i>:</p>
117 <dl compact>
118 <dd></dd>
119 <dt><i>LANG</i></dt>
120 <dd>Provide a default value for the internationalization variables that are unset or null. (See XBD <a href=
121 "../basedefs/V1_chap08.html#tag_08_02"><i>8.2 Internationalization Variables</i></a> the precedence of internationalization
122 variables used to determine the values of locale categories.)</dd>
123 <dt><i>LC_ALL</i></dt>
124 <dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd>
125 <dt><i>LC_CTYPE</i></dt>
126 <dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as
127 opposed to multi-byte characters in arguments).</dd>
128 <dt><i>LC_MESSAGES</i></dt>
129 <dd><br>
130 Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.</dd>
131 <dt><i>NLSPATH</i></dt>
132 <dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
133 Determine the location of messages objects and message catalogs. <img src="../images/opt-end.gif" alt="[Option End]" border=
134 "0"></dd>
135 </dl>
136 </blockquote>
137 <h4 class="mansect"><a name="tag_20_93_09" id="tag_20_93_09"></a>ASYNCHRONOUS EVENTS</h4>
138 <blockquote>
139 <p>Default.</p>
140 </blockquote>
141 <h4 class="mansect"><a name="tag_20_93_10" id="tag_20_93_10"></a>STDOUT</h4>
142 <blockquote>
143 <p>Not used.</p>
144 </blockquote>
145 <h4 class="mansect"><a name="tag_20_93_11" id="tag_20_93_11"></a>STDERR</h4>
146 <blockquote>
147 <p>The standard error shall be used only for diagnostic messages.</p>
148 </blockquote>
149 <h4 class="mansect"><a name="tag_20_93_12" id="tag_20_93_12"></a>OUTPUT FILES</h4>
150 <blockquote>
151 <p>None.</p>
152 </blockquote>
153 <h4 class="mansect"><a name="tag_20_93_13" id="tag_20_93_13"></a>EXTENDED DESCRIPTION</h4>
154 <blockquote>
155 <p>None.</p>
156 </blockquote>
157 <h4 class="mansect"><a name="tag_20_93_14" id="tag_20_93_14"></a>EXIT STATUS</h4>
158 <blockquote>
159 <p>The following exit values shall be returned:</p>
160 <dl compact>
161 <dd></dd>
162 <dt> 0</dt>
163 <dd>All <i>pathname</i> operands passed all of the checks.</dd>
164 <dt>>0</dt>
165 <dd>An error occurred.</dd>
166 </dl>
167 </blockquote>
168 <h4 class="mansect"><a name="tag_20_93_15" id="tag_20_93_15"></a>CONSEQUENCES OF ERRORS</h4>
169 <blockquote>
170 <p>Default.</p>
171 </blockquote>
172 <hr>
173 <div class="box"><em>The following sections are informative.</em></div>
174 <h4 class="mansect"><a name="tag_20_93_16" id="tag_20_93_16"></a>APPLICATION USAGE</h4>
175 <blockquote>
176 <p>The <a href="../utilities/test.html"><i>test</i></a> utility can be used to determine whether a given pathname names an existing
177 file; it does not, however, give any indication of whether or not any component of the pathname was truncated in a directory where
178 the _POSIX_NO_TRUNC feature is not in effect. The <i>pathchk</i> utility does not check for file existence; it performs checks to
179 determine whether a pathname does exist or could be created with no pathname component truncation.</p>
180 <p>The <i>noclobber</i> option in the shell (see the <a href="../utilities/V3_chap02.html#tag_19_26"><i>set</i></a> special
181 built-in) can be used to atomically create a file. As with all file creation semantics in the System Interfaces volume of
182 POSIX.1-2024, it guarantees atomic creation, but still depends on applications to agree on conventions and cooperate on the use of
183 files after they have been created.</p>
184 <p>To verify that a pathname meets the requirements of filename portability, applications should use both the <b>-p</b> and
185 <b>-P</b> options together.</p>
186 </blockquote>
187 <h4 class="mansect"><a name="tag_20_93_17" id="tag_20_93_17"></a>EXAMPLES</h4>
188 <blockquote>
189 <p>To verify that all pathnames in an imported data interchange archive are legitimate and unambiguous on the current system:</p>
190 <pre>
191 <tt># This example assumes that no pathnames in the archive
192 # contain <newline> characters.
193 pax -f archive | sed -e 's/[^[:alnum:]]/\\&/g' | xargs pathchk --
194 if [ $? -eq 0 ]
195 then
196 pax -r -f archive
197 else
198 echo Investigate problems before importing files.
199 exit 1
200 fi
201 </tt></pre>
202 <p>To verify that all files in the current directory hierarchy could be moved to any system conforming to the System Interfaces
203 volume of POSIX.1-2024 that also supports the <a href="../utilities/pax.html"><i>pax</i></a> utility:</p>
204 <pre>
205 <tt>find . -exec pathchk -p -P {} +
206 if [ $? -eq 0 ]
207 then
208 pax -w -f ../archive .
209 else
210 echo Portable archive cannot be created.
211 exit 1
212 fi
213 </tt></pre>
214 <p>To verify that a user-supplied pathname names a readable file and that the application can create a file extending the given
215 path without truncation and without overwriting any existing file:</p>
216 <pre>
217 <tt>case $- in
218 *C*) reset="";;
219 *) reset="set +C"
220 set -C;;
221 esac
222 test -r "$path" && pathchk "$path.out" &&
223 rm "$path.out" > "$path.out"
224 if [ $? -ne 0 ]; then
225 printf "%s: %s not found or %s.out fails \
226 creation checks.\n" $0 "$path" "$path"
227 $reset # Reset the noclobber option in case a trap
228 # on EXIT depends on it.
229 exit 1
230 fi
231 $reset
232 PROCESSING < "$path" > "$path.out"
233 </tt></pre>
234 <p>The following assumptions are made in this example:</p>
235 <ol>
236 <li>
237 <p><b>PROCESSING</b> represents the code that is used by the application to use <b>$path</b> once it is verified that
238 <b>$path.out</b> works as intended.</p>
239 </li>
240 <li>
241 <p>The state of the <i>noclobber</i> option is unknown when this code is invoked and should be set on exit to the state it was in
242 when this code was invoked. (The <b>reset</b> variable is used in this example to restore the initial state.)</p>
243 </li>
244 <li>
245 <p>Note the usage of:</p>
246 <pre>
247 <tt>rm "$path.out" > "$path.out"
248 </tt></pre>
249 <ol type="a">
250 <li>
251 <p>The <i>pathchk</i> command has already verified, at this point, that <b>$path.out</b> is not truncated.</p>
252 </li>
253 <li>
254 <p>With the <i>noclobber</i> option set, the shell verifies that <b>$path.out</b> does not already exist before invoking <a href=
255 "../utilities/rm.html"><i>rm</i></a>.</p>
256 </li>
257 <li>
258 <p>If the shell succeeded in creating <b>$path.out</b>, <a href="../utilities/rm.html"><i>rm</i></a> removes it so that the
259 application can create the file again in the <b>PROCESSING</b> step.</p>
260 </li>
261 <li>
262 <p>If the <b>PROCESSING</b> step wants the file to exist already when it is invoked, the:</p>
263 <pre>
264 <tt>rm "$path.out" > "$path.out"
265 </tt></pre>
266 <p>should be replaced with:</p>
267 <pre>
268 <tt>> "$path.out"
269 </tt></pre>
270 <p>which verifies that the file did not already exist, but leaves <b>$path.out</b> in place for use by <b>PROCESSING</b>.</p>
271 </li>
272 </ol>
273 </li>
274 </ol>
275 </blockquote>
276 <h4 class="mansect"><a name="tag_20_93_18" id="tag_20_93_18"></a>RATIONALE</h4>
277 <blockquote>
278 <p>The <i>pathchk</i> utility was new for the ISO POSIX-2:1993 standard. It, along with the <a href=
279 "../utilities/V3_chap02.html#set"><i>set</i></a> <b>-C</b>(<i>noclobber</i>) option added to the shell, replaces the <i>mktemp</i>,
280 <i>validfnam</i>, and <i>create</i> utilities that appeared in early proposals. All of these utilities were attempts to solve
281 several common problems:</p>
282 <ul>
283 <li>
284 <p>Verify the validity (for several different definitions of "valid") of a pathname supplied by a user, generated by an
285 application, or imported from an external source.</p>
286 </li>
287 <li>
288 <p>Atomically create a file.</p>
289 </li>
290 <li>
291 <p>Perform various string handling functions to generate a temporary filename.</p>
292 </li>
293 </ul>
294 <p>The <i>create</i> utility, included in an early proposal, provided checking and atomic creation in a single invocation of the
295 utility; these are orthogonal issues and need not be grouped into a single utility. Note that the <i>noclobber</i> option also
296 provides a way of creating a lock for process synchronization; since it provides an atomic <i>create</i>, there is no race between
297 a test for existence and the following creation if it did not exist.</p>
298 <p>Having a function like <a href="../functions/tmpnam.html"><i>tmpnam</i>()</a> in the ISO C standard is important in many
299 high-level languages. The shell programming language, however, has built-in string manipulation facilities, making it very easy to
300 construct temporary filenames. The names needed obviously depend on the application, but are frequently of a form similar to:</p>
301 <pre>
302 <b>$TMPDIR/</b><i>application_abbreviation</i><b>$$.</b><i>suffix</i><tt>
303 </tt></pre>
304 <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 used
305 with the shell <i>noclobber</i> option to create a file without risk of collisions, as long as applications trying to use the same
306 filename name space are cooperating on the use of files after they have been created.</p>
307 <p>For historical purposes, <b>-p</b> does not check for the use of the <hyphen-minus> character as the first character in a
308 component of the pathname, or for an empty <i>pathname</i> operand.</p>
309 </blockquote>
310 <h4 class="mansect"><a name="tag_20_93_19" id="tag_20_93_19"></a>FUTURE DIRECTIONS</h4>
311 <blockquote>
312 <p>None.</p>
313 </blockquote>
314 <h4 class="mansect"><a name="tag_20_93_20" id="tag_20_93_20"></a>SEE ALSO</h4>
315 <blockquote>
316 <p><a href="../utilities/V3_chap02.html#tag_19_07"><i>2.7 Redirection</i></a> , <a href=
317 "../utilities/V3_chap02.html#tag_19_26"><i>set</i></a> , <a href="../utilities/test.html#"><i>test</i></a></p>
318 <p>XBD <a href="../basedefs/V1_chap08.html#tag_08"><i>8. Environment Variables</i></a> , <a href=
319 "../basedefs/V1_chap12.html#tag_12_02"><i>12.2 Utility Syntax Guidelines</i></a> , <a href=
320 "../basedefs/limits.h.html"><i><limits.h></i></a></p>
321 </blockquote>
322 <h4 class="mansect"><a name="tag_20_93_21" id="tag_20_93_21"></a>CHANGE HISTORY</h4>
323 <blockquote>
324 <p>First released in Issue 4.</p>
325 </blockquote>
326 <h4 class="mansect"><a name="tag_20_93_22" id="tag_20_93_22"></a>Issue 7</h4>
327 <blockquote>
328 <p>Austin Group Interpretations 1003.1-2001 #039, #040, and #094 are applied.</p>
329 <p>SD5-XCU-ERN-121 is applied, updating the EXAMPLES section.</p>
330 <p>POSIX.1-2008, Technical Corrigendum 1, XCU/TC1-2008/0127 [291] is applied.</p>
331 <p>POSIX.1-2008, Technical Corrigendum 2, XCU/TC2-2008/0150 [584] and XCU/TC2-2008/0151 [584] are applied.</p>
332 </blockquote>
333 <h4 class="mansect"><a name="tag_20_93_23" id="tag_20_93_23"></a>Issue 8</h4>
334 <blockquote>
335 <p>Austin Group Defect 1122 is applied, changing the description of <i>NLSPATH .</i></p>
336 </blockquote>
337 <div class="box"><em>End of informative text.</em></div>
338 <hr>
339 <p> </p>
340 <a href="#top"><span class="topOfPage">return to top of page</span></a><br>
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