linux man page for hash

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

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 Vari-
	      ables.

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  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 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  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 Technol-
       ogy -- 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)