Unsetting an Alias

There will be times that you set a common command such as who with a new definition and then decide you need its old functionality back. You can quote, or protect, the alias name to temporarily override the alias, for example, \who. Or you can permanently regain the old functionality by unsetting the alias. To unset an alias use the unalias command. In one of the previous examples who was set to who | sort. To unset who, type:

unalias who

Then, type alias and notice from the listing that who has disappeared from the alias list and now performs it original function. The results of running who before and then after should look something like this:

$ who
mary       tty02        Sep 24 14:19
michael    tty04        Sep 24 09:41
nick       tty01        Sep 24 09:41
$ unalias who
$ who
nick       tty01        Sep 24 09:41
mary       tty02        Sep 24 14:19
michael    tty04        Sep 24 09:41
$

The POSIX and Korn Shells default aliases (i.e., false, integer, ...) can be unset or redefined, as well. The POSIX Shell also provides the -a option with the unalias built-in command. This option can be used to remove all the alias definitions by typing, at the shell command line prompt:

unalias -a