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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 differ (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 Section
       2.9.1.1, 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
       POSIX.1-2008, 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
                 <slash> characters, 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 vari-
                 ables that are unset or null. (See the Base Definitions  vol-
                 ume  of POSIX.1-2008, Section 8.2, Internationalization Vari-
                 ables 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 POSIX.1-2008,  Chapter  8,  Environment
                 Variables.
ASYNCHRONOUS EVENTS
       Default.
STDOUT
       The  standard output of hash shall be used when no arguments are speci-
       fied. Its format is unspecified, but  includes  the  pathname  of  each
       utility in the list of remembered locations for the current shell envi-
       ronment. 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  environ-
       ment.
       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  applica-
       tions,  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
       Section 2.9.1.1, Command Search and Execution
       The Base Definitions volume of  POSIX.1-2008,  Chapter  8,  Environment
       Variables, Section 12.2, Utility Syntax Guidelines
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/online.html .
       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,  see  https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                             HASH(1P)