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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

              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-defined.


       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 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






       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 .