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这是我的编程问题的修订版：

  1. 分叉两个运行随机时间的空闲进程，每个进程运行时间在 0 到 20 秒之间。
  2. 进程应使用信号 SIGSTOP 和 SIGCONT 将进程安排在循环队列中。
  3. 当子进程都为每个空闲进程终止时，父进程也应该终止。
  4. 如果其中一个子进程终止，它应该继续运行，直到它们都使用 SIGCHLD 终止。

这是关于我有多远。

#include <iostream>
#include <unistd.h>
#include <sys/wait.h>

using namespace std;
using std::cout;

volatile sig_atomic_t keep_going = 1;

void catch_child (int sig)
{ int status, p;
  p = waitpid(-1,&status,WNOHANG);
  if (p==0) return;
  keep_going=0;
  cout<<"Child process caught: "<< p <<endl;
  return;
}


int  main()
{
  pid_t pid;
  pid_t mypid;
  int rand1;

  rand1 = rand()%20;    

  signal (SIGCHLD, catch_child);

  pid = fork();
  if (pid<0) {
    cout<<"Error\n";
    return 0;
  }
  else if (pid==0) {


    mypid = getpid();
    cout << "Child pid is " << mypid << "\n";
    execlp("./idle","./idle","1",rand1,0);
  } else {
    mypid=getpid();

    cout<<"parent procss is "<<mypid<<" and child is "<<pid<<"\n";
    sleep(5);

    cout<<"pausing child "<<pid<<" for 5 seconds\n";
    kill(pid,SIGSTOP);

    for (int i=0; i<5; i++) sleep(1);

    cout<<"Resuming child "<<pid<<"\n";
    kill(pid,SIGCONT);

    cout<<"Parent process pid is "<<mypid<<" waiting for child to stop\n";
    while (keep_going==1) sleep(1);
    // wait(NULL);


    cout <<"Parent knows that Child now done\n";
  }
  return 0;
}
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