1MAN(1P) POSIX Programmer's Manual MAN(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 man — display system documentation
13
15 man [-k] name...
16
18 The man utility shall write information about each of the name oper‐
19 ands. If name is the name of a standard utility, man at a minimum shall
20 write a message describing the syntax used by the standard utility, its
21 options, and operands. If more information is available, the man util‐
22 ity shall provide it in an implementation-defined manner.
23 An implementation may provide information for values of name other than
25 the standard utilities. Standard utilities that are listed as optional
26 and that are not supported by the implementation either shall cause a
27 brief message indicating that fact to be displayed or shall cause a
28 full display of information as described previously.
29
31 The man utility shall conform to the Base Definitions volume of
32 POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
33 The following option shall be supported:
35 -k Interpret name operands as keywords to be used in searching a
37 utilities summary database that contains a brief purpose entry
38 for each standard utility and write lines from the summary
39 database that match any of the keywords. The keyword search
40 shall produce results that are the equivalent of the output of
41 the following command:
42 grep -Ei '
45 name
46 name
47 ...
48 ' summary-database
49 This assumes that the summary-database is a text file with a
51 single entry per line; this organization is not required and
52 the example using grep -Ei is merely illustrative of the type
53 of search intended. The purpose entry to be included in the
54 database shall consist of a terse description of the purpose of
55 the utility.
56
58 The following operand shall be supported:
59 name A keyword or the name of a standard utility. When -k is not
61 specified and name does not represent one of the standard
62 utilities, the results are unspecified.
63
65 Not used.
66
68 None.
69
71 The following environment variables shall affect the execution of man:
72 LANG Provide a default value for the internationalization vari‐
74 ables that are unset or null. (See the Base Definitions vol‐
75 ume of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
76 ables for the precedence of internationalization variables
77 used to determine the values of locale categories.)
78 LC_ALL If set to a non-empty string value, override the values of
80 all the other internationalization variables.
81 LC_CTYPE Determine the locale for the interpretation of sequences of
83 bytes of text data as characters (for example, single-byte as
84 opposed to multi-byte characters in arguments and in the sum‐
85 mary database). The value of LC_CTYPE need not affect the
86 format of the information written about the name operands.
87 LC_MESSAGES
89 Determine the locale that should be used to affect the format
90 and contents of diagnostic messages written to standard error
91 and informative messages written to standard output.
92 NLSPATH Determine the location of message catalogs for the processing
94 of LC_MESSAGES.
95 PAGER Determine an output filtering command for writing the output
97 to a terminal. Any string acceptable as a command_string op‐
98 erand to the sh -c command shall be valid. When standard out‐
99 put is a terminal device, the reference page output shall be
100 piped through the command. If the PAGER variable is null or
101 not set, the command shall be either more or another pagina‐
102 tor utility documented in the system documentation.
103
105 Default.
106
108 The man utility shall write text describing the syntax of the utility
109 name, its options and its operands, or, when -k is specified, lines
110 from the summary database. The format of this text is implementation-
111 defined.
112
114 The standard error shall be used for diagnostic messages, and may also
115 be used for informational messages of unspecified format.
116
118 None.
119
121 None.
122
124 The following exit values shall be returned:
125 0 Successful completion.
127 >0 An error occurred.
129
131 Default.
132 The following sections are informative.
134
136 None.
137
139 None.
140
142 It is recognized that the man utility is only of minimal usefulness as
143 specified. The opinion of the standard developers was strongly divided
144 as to how much or how little information man should be required to pro‐
145 vide. They considered, however, that the provision of some portable way
146 of accessing documentation would aid user portability. The arguments
147 against a fuller specification were:
148 * Large quantities of documentation should not be required on a sys‐
150 tem that does not have excess disk space.
151 * The current manual system does not present information in a manner
153 that greatly aids user portability.
154 * A ``better help system'' is currently an area in which vendors feel
156 that they can add value to their POSIX implementations.
157 The -f option was considered, but due to implementation differences, it
159 was not included in this volume of POSIX.1‐2017.
160 The description was changed to be more specific about what has to be
162 displayed for a utility. The standard developers considered it insuffi‐
163 cient to allow a display of only the synopsis without giving a short
164 description of what each option and operand does.
165 The ``purpose'' entry to be included in the database can be similar to
167 the section title (less the numeric prefix) from this volume of
168 POSIX.1‐2017 for each utility. These titles are similar to those used
169 in historical systems for this purpose.
170 See mailx for rationale concerning the default paginator.
172 The caveat in the LC_CTYPE description was added because it is not a
174 requirement that an implementation provide reference pages for all of
175 its supported locales on each system; changing LC_CTYPE does not neces‐
176 sarily translate the reference page into another language. This is
177 equivalent to the current state of LC_MESSAGES in POSIX.1‐2008—locale-
178 specific messages are not yet a requirement.
179 The historical MANPATH variable is not included in POSIX because no
181 attempt is made to specify naming conventions for reference page files,
182 nor even to mandate that they are files at all. On some implementations
183 they could be a true database, a hypertext file, or even fixed strings
184 within the man executable. The standard developers considered the
185 portability of reference pages to be outside their scope of work. How‐
186 ever, users should be aware that MANPATH is implemented on a number of
187 historical systems and that it can be used to tailor the search pattern
188 for reference pages from the various categories (utilities, functions,
189 file formats, and so on) when the system administrator reveals the
190 location and conventions for reference pages on the system.
191 The keyword search can rely on at least the text of the section titles
193 from these utility descriptions, and the implementation may add more
194 keywords. The term ``section titles'' refers to the strings such as:
195 man — Display system documentation
198 ps — Report process status
199
201 None.
202
204 more
205 The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment
207 Variables, Section 12.2, Utility Syntax Guidelines
208
210 Portions of this text are reprinted and reproduced in electronic form
211 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
212 table Operating System Interface (POSIX), The Open Group Base Specifi‐
213 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
214 Electrical and Electronics Engineers, Inc and The Open Group. In the
215 event of any discrepancy between this version and the original IEEE and
216 The Open Group Standard, the original IEEE and The Open Group Standard
217 is the referee document. The original Standard can be obtained online
218 at http://www.opengroup.org/unix/online.html .
219 Any typographical or formatting errors that appear in this page are
221 most likely to have been introduced during the conversion of the source
222 files to man page format. To report such errors, see https://www.ker‐
223 nel.org/doc/man-pages/reporting_bugs.html .
224IEEE/The Open Group 2017 MAN(1P)