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
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following option shall be supported:
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 'namename...
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 environment variables shall affect the execution of man:
Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for the precedence of internationalization variables used to
determine the values of locale categories.)
If set to a non-empty string value, override the values of
all the other internationalization variables.
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.
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.
Determine the location of message catalogs for the
processing of LC_MESSAGES.
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.
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
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
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
The -f option was considered, but due to implementation differences, it
was not included in this volume of IEEE Std 1003.1-2001.
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
IEEE Std 1003.1-2001 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
IEEE Std 1003.1-2001-locale-specific messages are not yet a
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 documentationps - Report process status
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html