# include<stdio.h>
# include<signal.h>
# include<unistd.h>
int wait_mark;
void waiting(),stop();
void main()
{ int  p1, p2;
signal(SIGINT,stop);
while((p1=fork())==-1);
if(p1>0)                            /*在父进程中*/
{
while((p2=fork())= =-1);
           if(p2>0)                    /*在父进程中*/
            {
                  wait_mark=1;
                 waiting(0);
                kill(p1,10);
                kill(p2,12);
                wait( );
               wait( );
               printf("parent process is killed!\n");
               exit(0);
            }
        else                        /*在子进程2中*/
           {
wait_mark=1;
signal(12,stop);
waiting();
lockf(1,1,0);
printf("child process 2 is killed by parent!\n");
lockf(1,0,0);
exit(0);
}
}
else                                /*在子进程1中*/
{
      wait_mark=1;
      signal(10,stop);
           waiting();
          lockf(1,1,0);
          printf("child process 1 is killed by parent!\n");
          lockf(1,0,0);
          exit(0);
}
}
void waiting()
{
   while(wait_mark!=0);
}
void stop()
{
   wait_mark=0;
}