创建一个孤儿进程组

 #include 
 #include 
 #include 
 #include 
 
 static void sig_hup(int signo)
 {
      printf("SIGHUP received, pid = %d\n", getpid());
 }
 
static void pr_ids(char* name)
{
     printf("%s: pid = %d, ppid = %d, pgrp = %d, tpgrp = %d\n",
         name, getpid(), getppid(), getpgrp(), tcgetpgrp(STDIN_FILENO));
 
     fflush(stdout);
 }
 int main()
{
     char c;
     pid_t pid;
 
     pr_ids("parent");
 
     if((pid = fork()) < 0)
     {
         printf("fork error");
     }
     else if(pid > 0)
     {
         sleep(5);
         exit(0);
     }
     else
     {
         pr_ids("child");
         signal(SIGHUP, sig_hup);
         kill(getpid(), SIGTSTP);
         pr_ids("child");
         if(read(STDIN_FILENO, &c, 1) != 1)
         {
             printf("read error from controlling TTY, errno =  %d\n", errno);
         }
         exit(0);
     }
}