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

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
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  locations  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  locations.  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,  Internationalization Vari-
              ables 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.
       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 arguments).
       LC_MESSAGES
              Determine the locale that should be used to  affect  the  format
              and contents of diagnostic 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 Def-
              initions  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  speci-
       fied.  Its  format  is  unspecified,  but includes the pathname of each
       utility in the list of remembered locations for the current shell envi-
       ronment.  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 sepa-
       rate 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 environ-
       ment.
       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 applica-
       tions, but may provide a performance improvement on a  few  implementa-
       tions; 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 original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                             HASH(1P)