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 (con-
       sult 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 Variables for the precedence of international-
              ization 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 stan-
              dard 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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                      HASH(1P)