getenvaddr.c

#include <stdlib.h>

int main(int argc, char *argv[])
{
   char *addr;
   if(argc < 2)
   {
      printf("Usage:\n%s <environment variable name>\n", argv[0]);
      exit(0);
   }
   addr = getenv(argv[1]);
   if(addr == NULL)
      printf("The environment variable %s doesn't exist.\n", argv[1]);
   else
      printf("%s is located at %p\n", argv[1], addr);
   return 0;
}