# unset

Unset a variable, cache variable, or environment variable.

    unset(<variable> [CACHE | PARENT_SCOPE])

Removes the specified variable causing it to become undefined. If `CACHE` is present then the variable is removed from the cache instead of the current scope.

If `PARENT_SCOPE` is present then the variable is removed from the scope above the current scope. See the same option in the `set()` command for further details.

`<variable>` can be an environment variable such as:

    unset(ENV{LD_LIBRARY_PATH})

in which case the variable will be removed from the current environment.