Remove variable or function names - the opposite of set.
Syntax unset [-fv] [name ...] Key -v Each name refers to a shell variable.(default) -f Each name refers to a shell function, and the function definition is removed.
$ unset myvariable
Each unset variable or function is removed from the environment passed to subsequent commands. If any of RANDOM, SECONDS, LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their special properties, even if they are subsequently reset.
The exit status is true unless a name is readonly. It is not an error for nothing to be unset.
unset is a bash built in command.
"Look Dave, I can see you're really upset about this" - HAL (Space 2001)
set - Set a variable