fs/open

52.js

var fs = require('fs');

fs.open('./my_file.txt', 'r', function opened(err, fd) {
  if (err) { throw err }

  var readBuffer = new Buffer(1024),
      bufferOffset = 0,
      bufferLength = readBuffer.length,
      filePosition = 100;

  fs.read(fd, readBuffer, bufferOffset, bufferLength, filePosition,
    function read(err, readBytes) {
      if (err) { throw err; }
      console.log('just read ' + readBytes + ' bytes');
      if (readBytes > 0) {
        console.log(readBuffer.slice(0, readBytes));
      }
    }
  );
});