1 #include 
     
       2 #include 
      
        3 #include 
       
         4  5  6 int main(void) 7 { 8     pid_t pid; 9     pid = fork();10     if(pid < 0){11         perror("fail to fock!\n");12         exit(-1);13     }14     else if(pid == 0){15         /*子进程*/16         printf("Sub-process,PID: %u,PPID: %u\n",getpid(),getppid());17     }18     else{19         /*父进程*/20         printf("Parent,PID: %u,Sub-process PID: %u\n",getpid(),pid);21         sleep(2);22     }23     return 0;24 }