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       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
       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 '

       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.




       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 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.

              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 .

       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.




       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-


       The standard error shall be used only for diagnostic messages.






       The following exit values shall be returned:

        0     Successful completion.

       >0     An error occurred.



       The following sections are informative.






       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 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 documentation
              ps - 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 .