filehandle.sync()

• 返回：<Promise> 成功时返回 undefined。

请求将所有打开文件描述符的数据刷新到存储设备。具体的实现取决于操作系统和设备。有关详细信息，请参考 POSIX fsync(2) 文档。

【Request that all data for the open file descriptor is flushed to the storage device. The specific implementation is operating system and device specific. Refer to the POSIX fsync(2) documentation for more detail.】