unset¶
Unset a variable, cache variable, or environment variable.
Unset Normal Variable or Cache Entry¶
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.
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.
Note
When evaluating 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.
Unset Environment Variable¶
unset(ENV{<variable>})
Removes <variable> from the currently available
Environment Variables.
Subsequent calls of $ENV{<variable>} will return the empty string.
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.