man(1p) — Linux manual page


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.1‐2017, 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

                   grep -Ei '
                   ' 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



       The following environment variables shall affect the execution of

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base
                 Definitions volume of POSIX.1‐2017, 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.

                 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.



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




EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.



       The following sections are informative.



EXAMPLES         top


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

       The -f option was considered, but due to implementation
       differences, it was not included in this volume of POSIX.1‐2017.

       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.1‐2017 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



SEE ALSO         top


       The Base Definitions volume of POSIX.1‐2017, 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 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       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 .

IEEE/The Open Group               2017                           MAN(1P)