Linux进程的创建和进程树

#include<stdio.h>
#include<sys/types.h>
#include<unistd.h>
int main()
{
	pid_t pid,pid1;
	pid=fork();
	pid1=fork();
	sleep(1);
	if(pid>0)
	{
		if(pid1>0)
			printf("This is the parent process,my pid is %d/n",getpid());
		else
			printf("This is the son2 process,my pid is %d,my father is %d/n",getpid(),getppid());
	}
	else
	{
		if(pid1>0)
			printf("This is the son1 process,my pid is %d,my father is %d/n",getpid(),getppid());
		else
			printf("This is the grandson process ,my pid is %d,my father is %d/n",getpid(),getppid());
	}
	exit(0);
}

运行结果如下：

This is the parent process,my pid is 2772

This is the son2 process,my pid is 2774,my father is 1

This is the son1 process,my pid is 2773,my father is 1

This is the grandson process ,my pid is 2775,my father is 1

再一次运行结果：

This is the parent process,my pid is 2787

This is the son1 process,my pid is 2788,my father is 2787

This is the grandson process ,my pid is 2790,my father is 1

This is the son2 process,my pid is 2789,my father is 1

由于父进程先于子进程结束，所以将子进程过继给init进程，就是1号进程。