CMake, like any other language, has variables. CMake variables are all treated as strings but they have the usual types.
To set a variable we use the set command and to use a variable we use the ${} notation:
set(VAR_NAME "value")
message("${VAR_NAME}")CMake variables names are case sensitive and a non-existent variable will always be replaced by an empty string. If we want to remove a variable, there is the unset command:
unset(VAR_NAME)We can even build variable names from other variables!
set(PLATFORM "LINUX")
set(HELLO_MESSAGE_WINDOWS "Hello Windows builders")
set(HELLO_MESSAGE_LINUX "Hello Linux builders")
message(${HELLO_MESSAGE_${PLATFORM}})CMake also has cache variables which are variables that survive between runs:
set(MY_CACHE_VAR "In the cache" CACHE STRING "Help text for MY_CACHE_VAR")We can override a cache variable by passing the -D flag in the cmake command:
cmake -D MY_CACHE_VAR="Overridden" ..We can do the usual finding and replacing in strings:
string(FIND "This is the from string" "string", FIND_RESULT)We don’t have to declare the variable FIND_RESULT before using the string command.
