main()
{
	char *s, *ttyname();

	if (isatty(0) == 0) {
		printf("Standard input not a tty.\en");
	}
	else {
		if ((s = ttyname(0)) == 0) 
			printf("Ttyname not found.\en");
		else 
			printf("You're on tty %s\en", s);
	}
}