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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
MAN(1P) POSIX Programmer's Manual MAN(1P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
man — display system documentation
man [−k] name...
The man utility shall write information about each of the name
operands. If name is the name of a standard utility, man at a minimum
shall write a message describing the syntax used by the standard
utility, its options, and operands. If more information is available,
the man utility shall provide it in an implementation-defined manner.
An implementation may provide information for values of name other
than the standard utilities. Standard utilities that are listed as
optional and that are not supported by the implementation either
shall cause a brief message indicating that fact to be displayed or
shall cause a full display of information as described previously.
The man utility shall conform to the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.
The following option shall be supported:
−k Interpret name operands as keywords to be used in searching a
utilities summary database that contains a brief purpose
entry for each standard utility and write lines from the
summary database that match any of the keywords. The keyword
search shall produce results that are the equivalent of the
output of the following command:
grep −Ei '
name
name
...
' summary-database
This assumes that the summary-database is a text file with a
single entry per line; this organization is not required and
the example using grep −Ei is merely illustrative of the type
of search intended. The purpose entry to be included in the
database shall consist of a terse description of the purpose
of the utility.
The following operand shall be supported:
name A keyword or the name of a standard utility. When −k is not
specified and name does not represent one of the standard
utilities, the results are unspecified.
Not used.
None.
The following environment variables shall affect the execution of
man:
LANG Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions
volume of POSIX.1‐2008, Section 8.2, Internationalization
Variables for the precedence of internationalization
variables used to determine the values of locale
categories.)
LC_ALL If set to a non-empty string value, override the values of
all the other internationalization variables.
LC_CTYPE Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte
as opposed to multi-byte characters in arguments and in the
summary database). The value of LC_CTYPE need not affect
the format of the information written about the name
operands.
LC_MESSAGES
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to
standard error and informative messages written to standard
output.
NLSPATH Determine the location of message catalogs for the
processing of LC_MESSAGES.
PAGER Determine an output filtering command for writing the
output to a terminal. Any string acceptable as a
command_string operand to the sh −c command shall be valid.
When standard output is a terminal device, the reference
page output shall be piped through the command. If the
PAGER variable is null or not set, the command shall be
either more or another paginator utility documented in the
system documentation.
Default.
The man utility shall write text describing the syntax of the utility
name, its options and its operands, or, when −k is specified, lines
from the summary database. The format of this text is implementation-
defined.
The standard error shall be used for diagnostic messages, and may
also be used for informational messages of unspecified format.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
None.
None.
It is recognized that the man utility is only of minimal usefulness
as specified. The opinion of the standard developers was strongly
divided as to how much or how little information man should be
required to provide. They considered, however, that the provision of
some portable way of accessing documentation would aid user
portability. The arguments against a fuller specification were:
* Large quantities of documentation should not be required on a
system that does not have excess disk space.
* The current manual system does not present information in a
manner that greatly aids user portability.
* A ``better help system'' is currently an area in which vendors
feel that they can add value to their POSIX implementations.
The −f option was considered, but due to implementation differences,
it was not included in this volume of POSIX.1‐2008.
The description was changed to be more specific about what has to be
displayed for a utility. The standard developers considered it
insufficient to allow a display of only the synopsis without giving a
short description of what each option and operand does.
The ``purpose'' entry to be included in the database can be similar
to the section title (less the numeric prefix) from this volume of
POSIX.1‐2008 for each utility. These titles are similar to those
used in historical systems for this purpose.
See mailx for rationale concerning the default paginator.
The caveat in the LC_CTYPE description was added because it is not a
requirement that an implementation provide reference pages for all of
its supported locales on each system; changing LC_CTYPE does not
necessarily translate the reference page into another language. This
is equivalent to the current state of LC_MESSAGES in
POSIX.1‐2008—locale-specific messages are not yet a requirement.
The historical MANPATH variable is not included in POSIX because no
attempt is made to specify naming conventions for reference page
files, nor even to mandate that they are files at all. On some
implementations they could be a true database, a hypertext file, or
even fixed strings within the man executable. The standard developers
considered the portability of reference pages to be outside their
scope of work. However, users should be aware that MANPATH is
implemented on a number of historical systems and that it can be used
to tailor the search pattern for reference pages from the various
categories (utilities, functions, file formats, and so on) when the
system administrator reveals the location and conventions for
reference pages on the system.
The keyword search can rely on at least the text of the section
titles from these utility descriptions, and the implementation may
add more keywords. The term ``section titles'' refers to the strings
such as:
man — Display system documentation
ps — Report process status
None.
more(1p)
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 MAN(1P)