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man.1p (8887B)


  1. '\" et
  2. .TH MAN "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
  3. .\"
  4. .SH PROLOG
  5. This manual page is part of the POSIX Programmer's Manual.
  6. The Linux implementation of this interface may differ (consult
  7. the corresponding Linux manual page for details of Linux behavior),
  8. or the interface may not be implemented on Linux.
  9. .\"
  10. .SH NAME
  11. man
  12. \(em display system documentation
  13. .SH SYNOPSIS
  14. .LP
  15. .nf
  16. man \fB[\fR-k\fB] \fIname\fR...
  17. .fi
  18. .SH DESCRIPTION
  19. The
  20. .IR man
  21. utility shall write information about each of the
  22. .IR name
  23. operands. If
  24. .IR name
  25. is the name of a standard utility,
  26. .IR man
  27. at a minimum shall write a message describing the syntax used by the
  28. standard utility, its options, and operands. If more information is
  29. available, the
  30. .IR man
  31. utility shall provide it in an implementation-defined manner.
  32. .P
  33. An implementation may provide information for values of
  34. .IR name
  35. other than the standard utilities. Standard utilities that are listed
  36. as optional and that are not supported by the implementation either
  37. shall cause a brief message indicating that fact to be displayed or
  38. shall cause a full display of information as described previously.
  39. .SH OPTIONS
  40. The
  41. .IR man
  42. utility shall conform to the Base Definitions volume of POSIX.1\(hy2017,
  43. .IR "Section 12.2" ", " "Utility Syntax Guidelines".
  44. .P
  45. The following option shall be supported:
  46. .IP "\fB\-k\fP" 8
  47. Interpret
  48. .IR name
  49. operands as keywords to be used in searching a utilities summary
  50. database that contains a brief purpose entry for each standard utility
  51. and write lines from the summary database that match any of the
  52. keywords. The keyword search shall produce results that are the
  53. equivalent of the output of the following command:
  54. .RS 8
  55. .sp
  56. .RS 4
  57. .nf
  58. grep -Ei \(aq
  59. \fIname
  60. name\fP
  61. \&...
  62. \&\(aq \fIsummary-database\fR
  63. .fi
  64. .P
  65. .RE
  66. .P
  67. This assumes that the
  68. .IR summary-database
  69. is a text file with a single entry per line; this organization is not
  70. required and the example using
  71. .IR grep
  72. .BR \-Ei
  73. is merely illustrative of the type of search intended. The purpose
  74. entry to be included in the database shall consist of a terse
  75. description of the purpose of the utility.
  76. .RE
  77. .SH OPERANDS
  78. The following operand shall be supported:
  79. .IP "\fIname\fR" 10
  80. A keyword or the name of a standard utility. When
  81. .BR \-k
  82. is not specified and
  83. .IR name
  84. does not represent one of the standard utilities, the results are
  85. unspecified.
  86. .SH STDIN
  87. Not used.
  88. .SH "INPUT FILES"
  89. None.
  90. .SH "ENVIRONMENT VARIABLES"
  91. The following environment variables shall affect the execution of
  92. .IR man :
  93. .IP "\fILANG\fP" 10
  94. Provide a default value for the internationalization variables that are
  95. unset or null. (See the Base Definitions volume of POSIX.1\(hy2017,
  96. .IR "Section 8.2" ", " "Internationalization Variables"
  97. for the precedence of internationalization variables used to determine
  98. the values of locale categories.)
  99. .IP "\fILC_ALL\fP" 10
  100. If set to a non-empty string value, override the values of all the
  101. other internationalization variables.
  102. .IP "\fILC_CTYPE\fP" 10
  103. Determine the locale for the interpretation of sequences of bytes of
  104. text data as characters (for example, single-byte as opposed to
  105. multi-byte characters in arguments and in the summary database). The
  106. value of
  107. .IR LC_CTYPE
  108. need not affect the format of the information written about the
  109. .IR name
  110. operands.
  111. .IP "\fILC_MESSAGES\fP" 10
  112. .br
  113. Determine the locale that should be used to affect the format and
  114. contents of diagnostic messages written to standard error and
  115. informative messages written to standard output.
  116. .IP "\fINLSPATH\fP" 10
  117. Determine the location of message catalogs for the processing of
  118. .IR LC_MESSAGES .
  119. .IP "\fIPAGER\fP" 10
  120. Determine an output filtering command for writing the output to a
  121. terminal. Any string acceptable as a
  122. .IR command_string
  123. operand to the
  124. .IR sh
  125. .BR \-c
  126. command shall be valid. When standard output is a terminal device, the
  127. reference page output shall be piped through the command. If the
  128. .IR PAGER
  129. variable is null or not set, the command shall be either
  130. .IR more
  131. or another paginator utility documented in the system documentation.
  132. .SH "ASYNCHRONOUS EVENTS"
  133. Default.
  134. .SH STDOUT
  135. The
  136. .IR man
  137. utility shall write text describing the syntax of the utility
  138. .IR name ,
  139. its options and its operands, or, when
  140. .BR \-k
  141. is specified, lines from the summary database. The format of this text
  142. is implementation-defined.
  143. .SH STDERR
  144. The standard error shall be used for diagnostic messages, and may also
  145. be used for informational messages of unspecified format.
  146. .SH "OUTPUT FILES"
  147. None.
  148. .SH "EXTENDED DESCRIPTION"
  149. None.
  150. .SH "EXIT STATUS"
  151. The following exit values shall be returned:
  152. .IP "\00" 6
  153. Successful completion.
  154. .IP >0 6
  155. An error occurred.
  156. .SH "CONSEQUENCES OF ERRORS"
  157. Default.
  158. .LP
  159. .IR "The following sections are informative."
  160. .SH "APPLICATION USAGE"
  161. None.
  162. .SH EXAMPLES
  163. None.
  164. .SH RATIONALE
  165. It is recognized that the
  166. .IR man
  167. utility is only of minimal usefulness as specified. The opinion of the
  168. standard developers was strongly divided as to how much or how little
  169. information
  170. .IR man
  171. should be required to provide. They considered, however, that the
  172. provision of some portable way of accessing documentation would aid
  173. user portability. The arguments against a fuller specification were:
  174. .IP " *" 4
  175. Large quantities of documentation should not be required on a system
  176. that does not have excess disk space.
  177. .IP " *" 4
  178. The current manual system does not present information in a manner that
  179. greatly aids user portability.
  180. .IP " *" 4
  181. A ``better help system'' is currently an area in which vendors feel
  182. that they can add value to their POSIX implementations.
  183. .P
  184. The
  185. .BR \-f
  186. option was considered, but due to implementation differences, it was
  187. not included in this volume of POSIX.1\(hy2017.
  188. .P
  189. The description was changed to be more specific about what has to be
  190. displayed for a utility. The standard developers considered it
  191. insufficient to allow a display of only the synopsis without giving a
  192. short description of what each option and operand does.
  193. .P
  194. The ``purpose'' entry to be included in the database can be similar to
  195. the section title (less the numeric prefix) from this volume of POSIX.1\(hy2017 for each utility.
  196. These titles are similar to those used in historical systems for this
  197. purpose.
  198. .P
  199. See
  200. .IR mailx
  201. for rationale concerning the default paginator.
  202. .P
  203. The caveat in the
  204. .IR LC_CTYPE
  205. description was added because it is not a requirement that an
  206. implementation provide reference pages for all of its supported locales
  207. on each system; changing
  208. .IR LC_CTYPE
  209. does not necessarily translate the reference page into another
  210. language. This is equivalent to the current state of
  211. .IR LC_MESSAGES
  212. in POSIX.1\(hy2008\(emlocale-specific messages are not yet a requirement.
  213. .P
  214. The historical
  215. .IR MANPATH
  216. variable is not included in POSIX because no attempt is made to specify
  217. naming conventions for reference page files, nor even to mandate that
  218. they are files at all. On some implementations they could be a true
  219. database, a hypertext file, or even fixed strings within the
  220. .IR man
  221. executable. The standard developers considered the portability of
  222. reference pages to be outside their scope of work. However, users
  223. should be aware that
  224. .IR MANPATH
  225. is implemented on a number of historical systems and that it can be
  226. used to tailor the search pattern for reference pages from the various
  227. categories (utilities, functions, file formats, and so on) when the
  228. system administrator reveals the location and conventions for reference
  229. pages on the system.
  230. .P
  231. The keyword search can rely on at least the text of the section titles
  232. from these utility descriptions, and the implementation may add more
  233. keywords. The term ``section titles'' refers to the strings such as:
  234. .sp
  235. .RS 4
  236. .nf
  237. man \(em Display system documentation
  238. ps \(em Report process status
  239. .fi
  240. .P
  241. .RE
  242. .SH "FUTURE DIRECTIONS"
  243. None.
  244. .SH "SEE ALSO"
  245. .IR "\fImore\fR\^"
  246. .P
  247. The Base Definitions volume of POSIX.1\(hy2017,
  248. .IR "Chapter 8" ", " "Environment Variables",
  249. .IR "Section 12.2" ", " "Utility Syntax Guidelines"
  250. .\"
  251. .SH COPYRIGHT
  252. Portions of this text are reprinted and reproduced in electronic form
  253. from IEEE Std 1003.1-2017, Standard for Information Technology
  254. -- Portable Operating System Interface (POSIX), The Open Group Base
  255. Specifications Issue 7, 2018 Edition,
  256. Copyright (C) 2018 by the Institute of
  257. Electrical and Electronics Engineers, Inc and The Open Group.
  258. In the event of any discrepancy between this version and the original IEEE and
  259. The Open Group Standard, the original IEEE and The Open Group Standard
  260. is the referee document. The original Standard can be obtained online at
  261. http://www.opengroup.org/unix/online.html .
  262. .PP
  263. Any typographical or formatting errors that appear
  264. in this page are most likely
  265. to have been introduced during the conversion of the source files to
  266. man page format. To report such errors, see
  267. https://www.kernel.org/doc/man-pages/reporting_bugs.html .