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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="man" id="man"></a> <a name="tag_20_77" id="tag_20_77"></a><!-- man -->
28 <h4 class="mansect"><a name="tag_20_77_01" id="tag_20_77_01"></a>NAME</h4>
29 <blockquote>man — display system documentation</blockquote>
30 <h4 class="mansect"><a name="tag_20_77_02" id="tag_20_77_02"></a>SYNOPSIS</h4>
31 <blockquote class="synopsis">
32 <div class="box"><code><tt><sup>[<a href="javascript:open_code('UP')">UP</a>]</sup> <img src="../images/opt-start.gif" alt=
33 "[Option Start]" border="0"> man</tt> <b>[</b><tt>-k</tt><b>]</b> <i>name</i><tt>... <img src="../images/opt-end.gif" alt=
34 "[Option End]" border="0"></tt></code></div>
35 </blockquote>
36 <h4 class="mansect"><a name="tag_20_77_03" id="tag_20_77_03"></a>DESCRIPTION</h4>
37 <blockquote>
38 <p>The <i>man</i> utility shall write information about each of the <i>name</i> operands. If <i>name</i> is the name of a standard
39 utility, <i>man</i> at a minimum shall write a message describing the syntax used by the standard utility, its options, operands,
40 environment variables affecting its execution, and its list of exit status codes. If more information is available, the <i>man</i>
41 utility shall provide it in an implementation-defined manner.</p>
42 <p>An implementation may provide information for values of <i>name</i> other than the standard utilities. Standard utilities that
43 are listed as optional and that are not supported by the implementation either shall cause a brief message indicating that fact to
44 be displayed or shall cause a full display of information as described previously.</p>
45 </blockquote>
46 <h4 class="mansect"><a name="tag_20_77_04" id="tag_20_77_04"></a>OPTIONS</h4>
47 <blockquote>
48 <p>The <i>man</i> utility shall conform to XBD <a href="../basedefs/V1_chap12.html#tag_12_02"><i>12.2 Utility Syntax
49 Guidelines</i></a> .</p>
50 <p>The following option shall be supported:</p>
51 <dl compact>
52 <dd></dd>
53 <dt><b>-k</b></dt>
54 <dd>Interpret <i>name</i> operands as keywords to be used in searching a utilities summary database that contains a brief purpose
55 entry for each standard utility and write lines from the summary database that match any of the keywords. The keyword search shall
56 produce results that are the equivalent of the output of the following command:
57 <pre>
58 <tt>grep -Ei '
59 </tt><i>name
60 name</i><tt>
61 ...
62 ' </tt><i>summary-database</i><tt>
63 </tt></pre>
64 <p>This assumes that the <i>summary-database</i> is a text file with a single entry per line; this organization is not required and
65 the example using <a href="../utilities/grep.html"><i>grep</i></a> <b>-Ei</b> is merely illustrative of the type of search
66 intended. The purpose entry to be included in the database shall consist of a terse description of the purpose of the utility.</p>
67 </dd>
68 </dl>
69 </blockquote>
70 <h4 class="mansect"><a name="tag_20_77_05" id="tag_20_77_05"></a>OPERANDS</h4>
71 <blockquote>
72 <p>The following operand shall be supported:</p>
73 <dl compact>
74 <dd></dd>
75 <dt><i>name</i></dt>
76 <dd>A keyword or the name of a standard utility. When <b>-k</b> is not specified and <i>name</i> does not represent one of the
77 standard utilities, the results are unspecified.</dd>
78 </dl>
79 </blockquote>
80 <h4 class="mansect"><a name="tag_20_77_06" id="tag_20_77_06"></a>STDIN</h4>
81 <blockquote>
82 <p>Not used.</p>
83 </blockquote>
84 <h4 class="mansect"><a name="tag_20_77_07" id="tag_20_77_07"></a>INPUT FILES</h4>
85 <blockquote>
86 <p>None.</p>
87 </blockquote>
88 <h4 class="mansect"><a name="tag_20_77_08" id="tag_20_77_08"></a>ENVIRONMENT VARIABLES</h4>
89 <blockquote>
90 <p>The following environment variables shall affect the execution of <i>man</i>:</p>
91 <dl compact>
92 <dd></dd>
93 <dt><i>LANG</i></dt>
94 <dd>Provide a default value for the internationalization variables that are unset or null. (See XBD <a href=
95 "../basedefs/V1_chap08.html#tag_08_02"><i>8.2 Internationalization Variables</i></a> for the precedence of internationalization
96 variables used to determine the values of locale categories.)</dd>
97 <dt><i>LC_ALL</i></dt>
98 <dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd>
99 <dt><i>LC_CTYPE</i></dt>
100 <dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as
101 opposed to multi-byte characters in arguments and in the summary database). The value of <i>LC_CTYPE</i> need not affect the format
102 of the information written about the <i>name</i> operands.</dd>
103 <dt><i>LC_MESSAGES</i></dt>
104 <dd><br>
105 Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error and
106 informative messages written to standard output.</dd>
107 <dt><i>NLSPATH</i></dt>
108 <dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
109 Determine the location of messages objects and message catalogs. <img src="../images/opt-end.gif" alt="[Option End]" border=
110 "0"></dd>
111 <dt><i>PAGER</i></dt>
112 <dd>Determine an output filtering command for writing the output to a terminal. Any string acceptable as a <i>command_string</i>
113 operand to the <a href="../utilities/sh.html"><i>sh</i></a> <b>-c</b> command shall be valid. When standard output is a terminal
114 device, the reference page output shall be piped through the command. If the <i>PAGER</i> variable is null or not set, the command
115 shall be either <a href="../utilities/more.html"><i>more</i></a> or another paginator utility documented in the system
116 documentation.</dd>
117 </dl>
118 </blockquote>
119 <h4 class="mansect"><a name="tag_20_77_09" id="tag_20_77_09"></a>ASYNCHRONOUS EVENTS</h4>
120 <blockquote>
121 <p>Default.</p>
122 </blockquote>
123 <h4 class="mansect"><a name="tag_20_77_10" id="tag_20_77_10"></a>STDOUT</h4>
124 <blockquote>
125 <p>The <i>man</i> utility shall write text describing the syntax of the utility <i>name</i>, its options and its operands, or, when
126 <b>-k</b> is specified, lines from the summary database. The format of this text is implementation-defined.</p>
127 </blockquote>
128 <h4 class="mansect"><a name="tag_20_77_11" id="tag_20_77_11"></a>STDERR</h4>
129 <blockquote>
130 <p>The standard error shall be used for diagnostic messages, and may also be used for informational messages of unspecified
131 format.</p>
132 </blockquote>
133 <h4 class="mansect"><a name="tag_20_77_12" id="tag_20_77_12"></a>OUTPUT FILES</h4>
134 <blockquote>
135 <p>None.</p>
136 </blockquote>
137 <h4 class="mansect"><a name="tag_20_77_13" id="tag_20_77_13"></a>EXTENDED DESCRIPTION</h4>
138 <blockquote>
139 <p>None.</p>
140 </blockquote>
141 <h4 class="mansect"><a name="tag_20_77_14" id="tag_20_77_14"></a>EXIT STATUS</h4>
142 <blockquote>
143 <p>The following exit values shall be returned:</p>
144 <dl compact>
145 <dd></dd>
146 <dt> 0</dt>
147 <dd>Successful completion.</dd>
148 <dt>>0</dt>
149 <dd>An error occurred.</dd>
150 </dl>
151 </blockquote>
152 <h4 class="mansect"><a name="tag_20_77_15" id="tag_20_77_15"></a>CONSEQUENCES OF ERRORS</h4>
153 <blockquote>
154 <p>Default.</p>
155 </blockquote>
156 <hr>
157 <div class="box"><em>The following sections are informative.</em></div>
158 <h4 class="mansect"><a name="tag_20_77_16" id="tag_20_77_16"></a>APPLICATION USAGE</h4>
159 <blockquote>
160 <p>None.</p>
161 </blockquote>
162 <h4 class="mansect"><a name="tag_20_77_17" id="tag_20_77_17"></a>EXAMPLES</h4>
163 <blockquote>
164 <p>None.</p>
165 </blockquote>
166 <h4 class="mansect"><a name="tag_20_77_18" id="tag_20_77_18"></a>RATIONALE</h4>
167 <blockquote>
168 <p>It is recognized that the <i>man</i> utility is only of minimal usefulness as specified. The opinion of the standard developers
169 was strongly divided as to how much or how little information <i>man</i> should be required to provide. They considered, however,
170 that the provision of some portable way of accessing documentation would aid user portability. The arguments against a fuller
171 specification were:</p>
172 <ul>
173 <li>
174 <p>Large quantities of documentation should not be required on a system that does not have excess disk space.</p>
175 </li>
176 <li>
177 <p>The current manual system does not present information in a manner that greatly aids user portability.</p>
178 </li>
179 <li>
180 <p>A "better help system" is currently an area in which vendors feel that they can add value to their POSIX implementations.</p>
181 </li>
182 </ul>
183 <p>The <b>-f</b> option was considered, but due to implementation differences, it was not included in this volume of
184 POSIX.1-2024.</p>
185 <p>The description was changed to be more specific about what has to be displayed for a utility. The standard developers considered
186 it insufficient to allow a display of only the synopsis without giving a short description of what each option and operand
187 does.</p>
188 <p>The "purpose" entry to be included in the database can be similar to the section title (less the numeric prefix) from this
189 volume of POSIX.1-2024 for each utility. These titles are similar to those used in historical systems for this purpose.</p>
190 <p>See <a href="../utilities/mailx.html"><i>mailx</i></a> for rationale concerning the default paginator.</p>
191 <p>The caveat in the <i>LC_CTYPE</i> description was added because it is not a requirement that an implementation provide reference
192 pages for all of its supported locales on each system; changing <i>LC_CTYPE</i> does not necessarily translate the reference page
193 into another language. This is equivalent to the current state of <i>LC_MESSAGES</i> in POSIX.1-2024—locale-specific messages are
194 not yet a requirement.</p>
195 <p>The historical <i>MANPATH</i> variable is not included in POSIX because no attempt is made to specify naming conventions for
196 reference page files, nor even to mandate that they are files at all. On some implementations they could be a true database, a
197 hypertext file, or even fixed strings within the <i>man</i> executable. The standard developers considered the portability of
198 reference pages to be outside their scope of work. However, users should be aware that <i>MANPATH</i> is implemented on a number of
199 historical systems and that it can be used to tailor the search pattern for reference pages from the various categories (utilities,
200 functions, file formats, and so on) when the system administrator reveals the location and conventions for reference pages on the
201 system.</p>
202 <p>The keyword search can rely on at least the text of the section titles from these utility descriptions, and the implementation
203 may add more keywords. The term "section titles" refers to the strings such as:</p>
204 <pre>
205 <tt>man — Display system documentation
206 ps — Report process status
207 </tt></pre></blockquote>
208 <h4 class="mansect"><a name="tag_20_77_19" id="tag_20_77_19"></a>FUTURE DIRECTIONS</h4>
209 <blockquote>
210 <p>If this utility is directed to display a pathname that contains any bytes that have the encoded value of a <newline>
211 character when <newline> is a terminator or separator in the output format being used, implementations are encouraged to
212 treat this as an error. A future version of this standard may require implementations to treat this as an error.</p>
213 </blockquote>
214 <h4 class="mansect"><a name="tag_20_77_20" id="tag_20_77_20"></a>SEE ALSO</h4>
215 <blockquote>
216 <p><a href="../utilities/more.html#"><i>more</i></a></p>
217 <p>XBD <a href="../basedefs/V1_chap08.html#tag_08"><i>8. Environment Variables</i></a> , <a href=
218 "../basedefs/V1_chap12.html#tag_12_02"><i>12.2 Utility Syntax Guidelines</i></a></p>
219 </blockquote>
220 <h4 class="mansect"><a name="tag_20_77_21" id="tag_20_77_21"></a>CHANGE HISTORY</h4>
221 <blockquote>
222 <p>First released in Issue 4.</p>
223 </blockquote>
224 <h4 class="mansect"><a name="tag_20_77_22" id="tag_20_77_22"></a>Issue 5</h4>
225 <blockquote>
226 <p>The FUTURE DIRECTIONS section is added.</p>
227 </blockquote>
228 <h4 class="mansect"><a name="tag_20_77_23" id="tag_20_77_23"></a>Issue 7</h4>
229 <blockquote>
230 <p>Austin Group Interpretation 1003.1-2001 #108 is applied, clarifying that informational messages may appear on standard
231 error.</p>
232 </blockquote>
233 <h4 class="mansect"><a name="tag_20_77_24" id="tag_20_77_24"></a>Issue 8</h4>
234 <blockquote>
235 <p>Austin Group Defect 190 is applied, marking the <i>man</i> utility as part of the User Portability Utilities option, and adding
236 a requirement for the message it writes for a standard utility to include the environment variables affecting its execution and its
237 list of exit status codes.</p>
238 <p>Austin Group Defect 251 is applied, encouraging implementations to report an error if a utility is directed to display a
239 pathname that contains any bytes that have the encoded value of a <newline> character when <newline> is a terminator or
240 separator in the output format being used.</p>
241 <p>Austin Group Defect 1122 is applied, changing the description of <i>NLSPATH .</i></p>
242 </blockquote>
243 <div class="box"><em>End of informative text.</em></div>
244 <hr>
245 <p> </p>
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