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
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 XBD
V1_chap12(7) .
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 XBD 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- [
XSI] Determine the location of message catalogs for the processing of LC_MESSAGES. PATH- Determine the location of utility , as described in XBD 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:
CONSEQUENCES OF ERRORS
Default.
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(1)
-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
XBD V1_chap08(7), V1_chap12(7)
CHANGE HISTORY
First released in Issue 2.
Issue 7
The hash utility is moved from the XSI
option to the Base.
POSIX.1-2008, Technical Corrigendum 1, XCU/TC1-2008/0093 [241] is applied.