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)

PROLOG         top

       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.

NAME         top

       man — display system documentation

SYNOPSIS         top

       man [−k] name...

DESCRIPTION         top

       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.

OPTIONS         top

       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.

OPERANDS         top

       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.

STDIN         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       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.

ASYNCHRONOUS EVENTS         top

       Default.

STDOUT         top

       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.

STDERR         top

       The standard error shall be used for diagnostic messages, and may
       also be used for informational messages of unspecified format.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       None.

EXAMPLES         top

       None.

RATIONALE         top

       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

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       more(1p)

       The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT         top

       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)