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MAN(1P)                    POSIX Programmer's Manual                   MAN(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

NAME
       man - display system documentation

SYNOPSIS
       man [-k] name...

DESCRIPTION
       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 utili-
       ties  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  previ-
       ously.

OPTIONS
       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:

       -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...

       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
       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
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       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 IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the prece-
              dence 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 exam-
              ple, 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 writ-
              ten 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
       Default.

STDOUT
       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
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0     Successful completion.

       >0     An error occurred.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       None.

EXAMPLES
       None.

RATIONALE
       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
       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  descrip-
       tion 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 pre-
       fix) from this volume of IEEE Std 1003.1-2001 for each utility. These titles are similar to those used in  his-
       torical 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  trans-
       late  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 requirement.

       The historical MANPATH variable is not included in POSIX because no attempt is made to specify  naming  conven-
       tions  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
       None.

SEE ALSO
       more

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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 .



IEEE/The Open Group                  2003                              MAN(1P)