text: #include "kernel/types.h"
  #include "user/user.h"
  
  int 
  main (){
      char buf[64];
  
      while(1) {
          int n = read(0, buf, sizeof(buf));
          if (n <= 0) {
              break;
          }
          write(1, buf, n);
      }
      
      exit(0);
  }