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
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
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 Technology
-- 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 .
