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 .

IEEE/The Open Group                                   2003                                               HASH(P)