#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;
}