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

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 util-
       ities.  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
       The man utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Sec-
       tion 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 com-
	      mand:

	      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, Inter-
	      nationalization 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 interna-
	      tionalization 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 argu-
	      ments and in the summary database).  The value of LC_CTYPE need not affect the for-
	      mat of the information written about the name operands.

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error and informative messages written to stan-
	      dard 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 provi-
       sion of some portable way of accessing documentation would aid user portability. The argu-
       ments 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 util-
       ity. 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-spe-
       cific 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 (utili-
       ties, functions, file formats, and so on) when the system administrator reveals the  loca-
       tion 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, 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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					   MAN(P)
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