pid_t require_pid(const char *name) {
	pid_t pid;
	if (read_pid(name,&pid)) {
		fprintf(stderr, "Error: cannot find sandbox %s\n", name);
		exit(1);
	}
	return pid;
}
pid_t require_pid(const char *name) {
	pid_t pid;
	if (read_pid(name,&pid)) {
		fprintf(stderr, "Error: cannot find sandbox %s\n", name);
		exit(1);
	}
	return pid;
}