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 variables that are unset or null. (See the
                 Base  Definitions  volume  of POSIX.1‐2008, 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 POSIX.1‐2008,
                 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

       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 Electrical 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 .

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       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
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