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 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.

       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 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
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .