PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

HASH(1P)                  POSIX Programmer's Manual                 HASH(1P)

PROLOG         top

       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         top

       hash — remember or report utility locations

SYNOPSIS         top

       hash [utility...]

       hash −r

DESCRIPTION         top

       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         top

       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         top

       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         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       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         top

       Default.

STDOUT         top

       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         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       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         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       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         top

       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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                            HASH(1P)