孤儿进程与僵尸进程

孤儿进程：父进程死了，子进程被init进程领养
僵尸进程：子进程死了，父进程没有回收子进程的资源（PCB）

如何回收僵尸进程：杀死父亲，由init进程领养，无法回收

orphan.c

#include<stdio.h>
#include<unistd.h>

int main()
{
     pid_t pid=fork();
     if(pid==0){
        while(1){
             printf("I am child,pid=%d,ppid=%d\n",getpid(),getppid());
             sleep(1);
        }
     }else if(pid>0){
        printf("I am parent,pid=%d,ppid=%d\n",getpid(),getppid());
        sleep(5);
        printf("I am parent,I will die\n");
    }
    return 0;
}

zombie.c

#include<stdio.h>
#include<unistd.h>

int main()
{
     pid_t pid=fork();
     if(pid==0){
         printf("I am child,pid=%d,ppid=%d\n",getpid(),getppid());
         sleep(5);
         printf("I am child,I will die\n");
     }
     }else if(pid>0){
          while(1){
             printf("I am parent,pid=%d,ppid=%d\n",getpid(),getppid());
             sleep(1);
           }
    }
    return 0;
}