If you want to learn the arcane ways of m4 (probably already available on your system if you're ever had to build from source a project that uses autotools) you

If you want to learn the arcane ways of m4 (probably already available on your system if you're ever had to build from source a project that uses autotools) you can use the include function without rolling your own with a bit of sed or awk. https://web.mit.edu/gnu/doc/html/m4_8.html https://web.mit.edu/gnu/doc/html/m4_8.html