/in/ex1.c: In function 'main':
/in/ex1.c:67:8: warning: implicit declaration of function 'getopt' [-Wimplicit-function-declaration]
  opt = getopt( argc, argv, optString );
        ^~~~~~
/in/ex1.c:75:27: error: 'optarg' undeclared (first use in this function)
     globalArgs.langCode = optarg;
                           ^~~~~~
/in/ex1.c:75:27: note: each undeclared identifier is reported only once for each function it appears in
/in/ex1.c:103:33: error: 'optind' undeclared (first use in this function)
  globalArgs.inputFiles = argv + optind;
                                 ^~~~~~