func: open_f(int argc, char **argv)
  
  {
  
  	int flags = 0;
  
  	int readonly = 0;
  
  	int growable = 0;
  
  	int c;
  
  
  
  	while ((c = getopt(argc, argv, "snrg")) != EOF) {
  
  		switch (c) {
  
  		case 's':
  
  			flags |= BDRV_O_SNAPSHOT;
  
  			break;
  
  		case 'n':
  
  			flags |= BDRV_O_NOCACHE;
  
  			break;
  
  		case 'r':
  
  			readonly = 1;
  
  			break;
  
  		case 'g':
  
  			growable = 1;
  
  			break;
  
  		default:
  
  			return command_usage(&open_cmd);
  
  		}
  
  	}
  
  
  
  	if (!readonly) {
  
              flags |= BDRV_O_RDWR;
  
          }
  
  
  
  	if (optind != argc - 1)
  
  		return command_usage(&open_cmd);
  
  
  
  	return openfile(argv[optind], flags, growable);
  
  }
  