Section: POSIX Programmer's Manual (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.
--- remember or report utility locations
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
utility shall conform to the Base Definitions volume of POSIX.1-2008,
, Utility Syntax Guidelines.
The following option shall be supported:
Forget all previously remembered utility locations.
The following operand shall be supported:
The name of a utility to be searched for and added to the list of
remembered locations. If
contains one or more
characters, the results are unspecified.
The following environment variables shall affect the execution of
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.)
If set to a non-empty string value, override the values of all the
other internationalization variables.
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).
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard error.
Determine the location of message catalogs for the processing of
Determine the location of
as described in the Base Definitions volume of POSIX.1-2008,
Chapter 8, Environment Variables.
The standard output of
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
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.
The following exit values shall be returned:
An error occurred.
CONSEQUENCES OF ERRORS
The following sections are informative.
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
utility may be implemented as an alias---for example,
in which case utilities found through normal command search are not
listed by the
The effects of
can also be achieved portably by resetting the value of
in the simplest form, this can be:
The use of
names is unnecessary for most applications, but may provide a
performance improvement on a few implementations; normally, the hashing
process is included by default.
, 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
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