int is_jid = ('%' == *argv[1]);
	int job_num = atoi(argv[1] + is_jid);
	struct job_t * job = (is_jid ? getjobjid(jobs, job_num) : getjobpid(jobs, job_num));

	/*if argv[0] is "bg"*/
	if(!strcmp(argv[0], "bg")) {
		if (job->state == ST)
			if (kill(job->pid, SIGCONT))
				unix_error("kill error: SIGCONT");
	}

	/*if argv[0] is fg*/
	else
		waitfg(fgpid(jobs));

	return;