实现两个程序mysignal、mycontrl，mycontrl给mysignal发送SIGINT信号，控制mysignal是否在屏幕打印“hello”字符串。

int status = 0;

void catch_Signal(int Sign)
{
`	switch (Sign)
	{
 	 case SIGINT:
 		 if (status == 0)
 			 status = 1;
 		 else
 			status = 0;
 		 break;
	}
}

int singnal1(int signo, void (*func)(int))
{
    struct sigaction act, oact;
    act.sa_handler = func;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
    return sigaction(signo, &act, &oact);
}

int main(void)
{
	singnal1(SIGINT, catch_Signal);

	while (1)
	{
		if (status)
		{
			printf("hello\n");
		}
		sleep(1);
	}

	return EXIT_SUCCESS;
}

int main(int arg, char *args[])
{
	if (arg < 2)
	{
		return 0;
	}
	else
	{
		int pid = atoi(args[1]);
		kill(pid, SIGINT);
	}
	return EXIT_SUCCESS;
}