NAME

unalias - remove alias definitions

SYNOPSIS

unalias alias-name...

unalias -a


DESCRIPTION

The unalias utility shall remove the definition for each alias name specified. See Alias Substitution. The aliases shall be removed from the current shell execution environment; see Shell Execution Environment.

OPTIONS

The unalias utility shall conform to XBD Utility Syntax Guidelines.

The following option shall be supported:

-a

Remove all alias definitions from the current shell execution environment.

OPERANDS

The following operand shall be supported:

alias-name

The name of an alias to be removed.

STDIN

Not used.

INPUT FILES

None.

ENVIRONMENT VARIABLES

The following environment variables shall affect the execution of unalias:

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.

ASYNCHRONOUS EVENTS

Default.

STDOUT

Not used.

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

One of the alias-name operands specified did not represent a valid alias definition, or an error occurred.

CONSEQUENCES OF ERRORS

Default.

APPLICATION USAGE

Since unalias affects the current shell execution environment, it is generally provided as a shell regular built-in.

EXAMPLES

None.

RATIONALE

The unalias description is based on that from historical KornShell implementations. Known differences exist between that and the C shell. The KornShell version was adopted to be consistent with all the other KornShell features in this volume of POSIX.1-2017, such as command line editing.

The -a option is the equivalent of the unalias * form of the C shell and is provided to address security concerns about unknown aliases entering the environment of a user (or application) through the allowable implementation-defined predefined alias route or as a result of an ENV file. (Although unalias could be used to simplify the "secure" shell script shown in the command rationale, it does not obviate the need to quote all command names. An initial call to unalias -a would have to be quoted in case there was an alias for unalias.)

FUTURE DIRECTIONS

None.

SEE ALSO

Shell Command Language, alias

XBD Environment Variables, Utility Syntax Guidelines

CHANGE HISTORY

First released in Issue 4.

Issue 6

This utility is marked as part of the User Portability Utilities option.

Issue 7

The unalias utility is moved from the User Portability Utilities option to the Base. User Portability Utilities is now an option for interactive utilities.