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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 dif-
       fer (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 loca-
       tions  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 con-
              tains 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 prece-
              dence 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 exam-
              ple, 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  writ-
              ten 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 improve-
       ment 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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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)