example.nix

with import <nixpkgs> {};

let
  source = lib.writeFile "something.cc" ''
    #include <stdio.h>
    
    int main(void) { printf("%d\n", 42); return 0; }
  '';
in
stdenv.mkDerivation {
  name = "example";
  
  phases = [ "buildPhase" ];
  
  buildPhase = ''
    mkdir -p $out/bin
    cc -o $out/bin/example ${source}
  '';
}