进程的先后

#include
#include
#include
#include
int main(void)
{
	pid_t resut;
	resut=fork();

	 if(resut ==0)
	{
		

		printf(" this is in the child  progress \n ");

		printf("my father PID is %d \n", getppid());
		
		printf("my PID is %d \n", getpid());
		printf(" i  will exec the ps cAommand \n");
	//	exit (0);
	//	if((execlp("ps","ps","-ef",NULL))<0)
	//	{
	//		printf(" this is erro \n");
	//	}
	}
    	else if(resut>0)
	{
		printf(" this is in the father progress \n ");
		printf("my chiled PID is %d \n", resut);
		printf("my PID is %d \n", getpid());
		sleep(10);//  if father die ,but the child  still live .the pid of father  that the chidl want get by getppid() will erro
		//exit(0);
	}
	return 0;
}

注意注释部分

如果我们取消注释可能会出现错我.

因为父进程可能先于子进程结束一因此getppid()不能正确获得PID
now  父进程运行完自己的代码就结束了,这就是父进程先于子进程完活.