APUE习题9.2

/*Program:
 *      APUE习题9.2
 * History:
 *      2021/1/21       Chen Ying-jun   First release
 * */
#include<apue.h>
#include<iostream>
#include<my_error.h>
#include<unistd.h>

using namespace std;

int main(){

        pid_t pid,pgrp;

        if((pid=fork())<0)
                err_sys("fork error");
        else if(pid==0){//child

                int sessionPid;
                //build session
                if((sessionPid=setsid())<0)
                        err_sys("setsid error");

                cout<<"process id of session="<<sessionPid<<endl;    
                cout<<"foreground process group id="<<tcgetpgrp(STDIN_FILENO)<<endl;
                cout<<"foreground process group id="<<tcgetpgrp(STDOUT_FILENO)<<endl;
                cout<<"foreground process group id="<<tcgetpgrp(STDERR_FILENO)<<endl;
        }else{
                //使子进程先运行，以建立会话
                sleep(3);

                if((pgrp=getpgid(pid))<0)
                        err_sys("setid error");
    
                cout<<"child process id="<<pid<<endl;
                cout<<"group id of child process="<<pgrp<<endl;
        }

        exit(0);
}

运行结果：
process id of session=3465
foreground process group id=-1
foreground process group id=-1
foreground process group id=-1
child process id=3465
group id of child process=3465

子进程id=会话id（即会话首进程id）=子进程所在进程组id。
所有获取控制终端的组id全部返回出错，说明该进程组不是前台进程，没有控制终端。
和题目预期相符。

标签：group,APUE,process,pid,进程,习题,include,id,9.2
来源： https://blog.csdn.net/weixin_42614575/article/details/112981299