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HASH(1P) POSIX Programmer's Manual HASH(1P)
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.
hash — remember or report utility locations
hash [utility...]
hash −r
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.
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.
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.
Not used.
None.
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.
Default.
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.
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
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.
None.
None.
None.
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
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)
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