利用fork创建子进程

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

int main()
{
    int pid=fork();//创建子进程

    if(pid==0)
    {   
    
        printf("D:%d\t  %d\n",getppid(),getpid());return 0;//子进程结束
    }   
    
    int pid2=fork();//创建子进程
    if(pid2==0)
    {   
        printf("C:%d\t  %d\n",getppid(),getpid());waitpid(pid2,NULL,0);return 0;//子进程结束
    }   
    int pid3=fork();
    if(pid3==0)//创建子进程
    {   
        printf("B:%d\t  %d\n",getppid(),getpid());return 0;//子进程结束

    }   
    printf("父进程id   当前进程id\n");  
    printf("A:%d\t  %d\n",getppid(),getpid());
    waitpid(pid,NULL,0);waitpid(pid2,NULL,0);waitpid(pid3,NULL,0);//等待子进程结束;
    return 0;
}

父进程id   当前进程id
A:3195      6051
D:6051      6052
C:6051      6053
B:6051      6054

#include<stdio.h>
#include<unistd.h>
#include<wait.h>
#include<stdlib.h>
int main()
{

    int pid=fork();int pid3;
    if(pid==0)
    {   
        printf("C:%d\t  %d\n",getppid(),getpid());return 0;
    }   
    int pid2=fork();
    if(pid2==0)
    {   
        pid3=fork();
        if (pid3==0)
        {
            printf("D:%d\t  %d\n",getppid(),getpid());return 0;
        }
        else
        {
            printf("B:%d\t  %d\n",getppid(),getpid());return 0;
        }
    }   
    
        printf("父进程id  当前进程id\n");
        printf("A:%d\t  %d\n",getppid(),getpid());
        waitpid(pid,NULL,0);waitpid(pid2,NULL,0);waitpid(pid3,NULL,0);
        return 0;
    
}

父进程id  当前进程id
A:3195      6071
C:6071      6072
B:6071      6073
D:6073      6074