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

//测试前台进程组
//分为前台进程组和后台进程组，按ctrl+c时前台进程组将被kill。
int main(void)
{
    pid_t group1, group2;
    //创建进程组1，父进程作为组长进程
    setpgid(getpid(), getpid());
    group1 = getpgid(getpid());

    pid_t pid;
    int i = 0;

    for(; i< 3; i++){
        pid = fork();
        if(pid < 0){
            perror("fork error");
            exit(1);
        }else if(pid > 0){ //parent process
            if(i == 0 ){
                 //创建进程组2
                 setpgid(pid, pid);
                 group2 = getpgid(pid);
                 //将group2设置为前台进程组
                 tcsetpgrp(0, group2);
            }
            if(i == 1){
                //将第2个子进程加入到group2
                setpgid(pid, group2);
            }
            if(i == 2){
                //第3个子进程加入group1
                setpgid(pid, group1);
            }
        }else{ //child process
            if(i == 0){
                 //创建进程组2
                 setpgid(getpid(), getpid());
                 group2 = getpgid(getpid());
                 //将group2设置为前台进程组
                 tcsetpgrp(0, group2);
            }
            if(i == 1){
                //将第2个子进程加入到group2
                setpgid(getpid(), group2);
            }
            if(i == 2){
                //第3个子进程加入group1
                setpgid(getpid(), group1);
            }
        
            break;  //进程扇，子进程须退出
        }
    }

    printf("pid: %d, ppid: %d, pgid: %d\n",
            getpid(), getppid(), getpgid(0));
    
    pause();
 
    return 0;
}