static void sigchld(int unused);

	/* clean up child processes immediately */
	sigchld(0);

sigchld(int unused)
{
	if (signal(SIGCHLD, sigchld) == SIG_ERR) {
		perror("can't install SIGCHLD handler");
		exit(EXIT_FAILURE);
	}
	while (0 < waitpid(-1, NULL, WNOHANG))
		;
}
void