How to reuse code in CMake

Question

I've got the following piece of code which gets the current system IP and stores it in the SERVER_IP variable:

EXECUTE_PROCESS(
    COMMAND ip route get 8.8.8.8
    COMMAND awk "NR==1 {print $NF}"
    OUTPUT_VARIABLE SERVER_IP
    OUTPUT_STRIP_TRAILING_WHITESPACE
)

I need to use this IP several places in my CMakeLists.txt file hierarchy. What's the best approach to reuse this code? My first thought is to make it a function like function(GetIP), but I am not sure where to put this function to make it visible to all CMakeLists.txt file.

Answer 1

If you make the CMake function available in the top-level CMakeLists.txt file, it will be also available in the CMakeLists.txt files of the subdirectories you added with ADD_SUBDIRECTORY.

Either define the function directly in the top-level CMakeLists.txt file or use something like INCLUDE(GetIP.cmake) there.