| unset |
| ----- |
| |
| Unset a variable, cache variable, or environment variable. |
| |
| :: |
| |
| unset(<variable> [CACHE | PARENT_SCOPE]) |
| |
| Removes a normal variable from the current scope, causing it |
| to become undefined. If ``CACHE`` is present, then a cache variable |
| is removed instead of a normal variable. Note that when evaluating |
| :ref:`Variable References` of the form ``${VAR}``, CMake first searches |
| for a normal variable with that name. If no such normal variable exists, |
| CMake will then search for a cache entry with that name. Because of this |
| unsetting a normal variable can expose a cache variable that was previously |
| hidden. To force a variable reference of the form ``${VAR}`` to return an |
| empty string, use ``set(<variable> "")``, which clears the normal variable |
| but leaves it defined. |
| |
| If ``PARENT_SCOPE`` is present then the variable is removed from the scope |
| above the current scope. See the same option in the :command:`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. |