fs.createReadStream()

fs.createReadStream(path[, options])

Returns a new ReadStream object. (See Readable Stream).

Be aware that, unlike the default value set for highWaterMark on a readable stream (16 kb), the stream returned by this method has a default value of 64 kb for the same parameter.

options is an object or string with the following defaults:

{
  flags: 'r',
  encoding: null,
  fd: null,
  mode: 0o666,
  autoClose: true
}

options can include start and end values to read a range of bytes from the file instead of the entire file. Both start and end are inclusive and start at 0. The encoding can be any one of those accepted by Buffer.

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

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

mode sets the file mode (permission and sticky bits), but only if the file was created.

An example to read the last 10 bytes of a file which is 100 bytes long:

fs.createReadStream('sample.txt', {start: 90, end: 99});

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