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Diffstat (limited to 'Help/command/unset.rst')
| -rw-r--r-- | Help/command/unset.rst | 34 |
1 files changed, 25 insertions, 9 deletions
diff --git a/Help/command/unset.rst b/Help/command/unset.rst index a1fc95cc6..75210521e 100644 --- a/Help/command/unset.rst +++ b/Help/command/unset.rst @@ -3,23 +3,39 @@ unset Unset a variable, cache variable, or environment variable. -:: +Unset Normal Variable or Cache Entry +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. code-block:: cmake 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. +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 Environment Variable +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. code-block:: cmake -:: + unset(ENV{<variable>}) - unset(ENV{LD_LIBRARY_PATH}) +Removes ``<variable>`` from the currently available +:manual:`Environment Variables <cmake-env-variables(7)>`. +Subsequent calls of ``$ENV{<variable>}`` will return the empty string. -in which case the variable will be removed from the current -environment. +This command affects only the current CMake process, not the process +from which CMake was called, nor the system environment at large, +nor the environment of subsequent build or test processes. |