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Linux 2.6 - man page for hash (linux section 1posix)

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

NAME
       hash - remember or report utility locations

SYNOPSIS
       hash [utility...]

       hash -r


DESCRIPTION
       The  hash  utility  shall affect the way the current shell environment remembers the loca-
       tions of utilities found as described in Command Search and Execution . Depending  on  the
       arguments specified, it shall add utility locations to its list of remembered locations or
       it shall purge the contents of the list. When no arguments are specified, it shall  report
       on the contents of the list.

       Utilities provided as built-ins to the shell shall not be reported by hash.

OPTIONS
       The  hash  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:

       -r     Forget all previously remembered utility locations.

OPERANDS
       The following operand shall be supported:

       utility
	      The name of a utility to be searched for and added to the list of remembered  loca-
	      tions. If utility contains one or more slashes, the results are unspecified.

STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of hash:

       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).

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error.

       NLSPATH
	      Determine the location of message catalogs for the processing of LC_MESSAGES .

       PATH   Determine the location of utility, as described in the Base Definitions  volume  of
	      IEEE Std 1003.1-2001, Chapter 8, Environment Variables.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       The  standard  output of hash shall be used when no arguments are specified. Its format is
       unspecified, but includes the pathname of each utility in the list of remembered locations
       for  the  current  shell  environment. This list shall consist of those utilities named in
       previous hash invocations that have been invoked, and may contain those invoked and  found
       through the normal command search process.

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
       Since  hash  affects  the  current shell execution environment, it is always provided as a
       shell regular built-in. If it is called in a separate utility execution environment,  such
       as one of the following:

	      nohup hash -r
	      find . -type f | xargs hash

       it does not affect the command search process of the caller's environment.

       The  hash  utility  may	be implemented as an alias-for example, alias -t -, in which case
       utilities found through normal command search are not listed by the hash command.

       The effects of hash -r can also be achieved portably by resetting the value of PATH  ;  in
       the simplest form, this can be:

	      PATH="$PATH"

       The use of hash with utility names is unnecessary for most applications, but may provide a
       performance improvement on  a  few  implementations;  normally,	the  hashing  process  is
       included by default.

EXAMPLES
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Command Search and Execution

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					  HASH(P)


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