用FATFS写一个文件到SD卡中，比如WR.txt,内容为“THIS IS APPLE”,如果想在这个文件中续写一个“THIS IS APPLE”，应该如何操作？？？

fresult = f_open(&g_sFileObject, g_cCmdBuf, FA_READ | FA_CREATE_ALWAYS | FA_WRITE);
    f_sync (&g_sFileObject);
    if(fresult == FR_OK)
    {
      UARTprintf(" f_open is ok ");
      fresult = f_write (&g_sFileObject, buf1, sizeof (buf1) - 1, &bytesWritten);
      f_sync (&g_sFileObject);

      if(fresult == FR_OK)
      {
        UARTprintf(" f_write is ok ");
        UARTprintf("%d ",bytesWritten);
      }
      else
      {
        UARTprintf(" f_write is fail ");
      }
    }
    else
    {
      UARTprintf(" f_open is fail ");
    } 此帖出自小平头技术问答