#include <stdio.h>
#include <stdlib.h>

void main (int argc, char **argv) {
   char *answer;
   switch (argc) {
      case 0: printf ("This can't happen.\n");
              break;
      case 1: printf ("No args to program %s.\n", argv[0]);
              break;
      case 2: answer = getenv(argv[1]);
              if (answer)
                 printf ("%s evaluates to %s.\n", argv[1], answer);
              else
                 printf ("%s undefined.\n", argv[1]);
              break;
      default: printf ("Too many args.\n");
      }
   }