options may also include a start option to allow writing data at some position past the beginning of the file, allowed values are in the [0, Number.MAX_SAFE_INTEGER] range. Modifying a file rather than replacing it may require the flags option to be set to r+ rather than the default w. The encoding can be any one of those accepted by Buffer.

If autoClose is set to true (default behavior) on 'error' or 'finish'the file descriptor will be closed automatically. If autoClose is false, then the file descriptor won't be closed, even if there's an error. It is the application's responsibility to close it and make sure there's no file descriptor leak.

By default, the stream will emit a 'close' event after it has been destroyed. Set the emitClose option to false to change this behavior.

By providing the fs option it is possible to override the corresponding fsimplementations for open, write, writev, and close. Overriding write()without writev() can reduce performance as some optimizations (_writev()) will be disabled. When providing the fs option, overrides for at least one ofwrite and writev are required. If no fd option is supplied, an override for open is also required. If autoClose is true, an override for closeis also required.

Like fs.ReadStream, if fd is specified, fs.WriteStream will ignore thepath argument and will use the specified file descriptor. This means that no'open' event will be emitted. fd should be blocking; non-blocking fds should be passed to net.Socket.

If options is a string, then it specifies the encoding.