text: #include <sys/types.h>
  #include <sys/stat.h>
  #include <fcntl.h>
  #include <stdio.h>
  #include <unistd.h>  
  
  int main(void)
  {
      int fd;
      int res;
      char buf[] = "Houmin says hello to scull!";
      int buflen = sizeof(buf);
      char buf2[100];
      fd = open("/dev/scull0", O_RDWR);
      if (fd < 0) {
          printf("Open scull device failed\n");
      }
  
      res = write(fd, buf, buflen);
      printf("Write to scull device, content: %s\n", buf);
  
      lseek(fd, 0, SEEK_SET);
      res = read(fd, buf2, buflen);
      buf2[buflen] = '\0';
      printf("Read from scull device: %s\n", buf2);
  
      close(fd);
      return 0;
  }
  