20230802

 终端时间显示，n中断时间显示

2023-08-02 21:07:55
2023-08-02 21:07:56
2023-08-02 21:07:57
2023-08-02 21:07:58
n
child=n  end!!!!!!!!!!
ubuntu@ubuntu:D5$ cat k3.c
#include <head.h>

void gettime();
void gettime()
{
	time_t t1;
	time(&t1);
	struct tm* info = localtime(&t1);

	printf("%4d-%02d-%02d %02d:%02d:%02d\n",\
			info->tm_year+1900,info->tm_mon+1,info->tm_mday,\
			info->tm_hour,info->tm_min,info->tm_sec);
}

int main()
{
	char s1;
	pid_t cpid = fork();
	if(cpid > 0)
	{
		while(1)
		{
			sleep(1);
			pid_t c1 = waitpid(-1,NULL,WNOHANG);
			if(c1 > 0)
			{
				return 0;
			}
			else
			{
				gettime();
			}
		}

	} 
	else if(0 == cpid)
	{
		while(1)
		{
			scanf("%s",&s1);
			printf("child=%s  ",&s1);
			if(s1 == 'n')
			{
				printf("end!!!!!!!!!!\n");
				exit(0);
			}
		}

	}
	else
	{
		perror("fork");
		return -1;
	}


	return 0;

}

守护进程

#include <head.h>

int main()
{
	pid_t cpid = fork();

	if(0 == cpid)
	{
		pid_t sid = setsid();
		printf("%d",sid);

		chdir("/");

		umask(0);

		for(int i=0;i<getdtablesize();i++)
			close(i);

		while(1)
		{
		sleep(1);
		}
	}

	return 0;
}