#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <set>
#include <sys/wait.h>

using namespace std;

int main(int argc, char const *argv[])
{
    int num = 5;
    set<int> pid_set;
    int seq = 0;
    pid_t temp_pid;

    for (int i=0; i < num; i++)
    {
        temp_pid = fork();
        if (temp_pid ==0 || temp_pid == -1)
            break;

        pid_set.insert(temp_pid);
        seq++;
    }

    if (temp_pid == 0)
    {
        for (int j=0; j < 10; j++)
        {
            printf("%d---%d---%d\n", getpid(), j, seq);
            if (seq == 0)
            {
                char *p = NULL;
                printf("%c", *p);
            }
            sleep(seq);
        }
        return 0;
    }

    else
    {
        int stat = 0;
        int ret = 0;

        while(true){
            ret = waitpid(0, &stat, WNOHANG);
            if (ret > 0)
            {
                set<int>::iterator position = pid_set.find(ret);
                if (position != pid_set.end())
                    pid_set.erase(position);
                if (WIFSIGNALED(stat))
                    printf("term %d, %d\n", ret, WTERMSIG(stat));
                if (WIFEXITED(stat))
                    printf("exit %d, %d\n", ret, WEXITSTATUS(stat));
            }

            if (pid_set.size() == 0)
            {
                exit(0);
            }
        }

    }


    return 0;
}