Create stream with on(open) callback

gistfile1.txt

var fs = require('fs');

var createStream = function(type, path, erred, opened) {
  var StreamType = (type === 'read')
    ? 'createReadStream'
    : 'createWriteStream';

  if (typeof(opened) !== 'function') {
    opened = erred;
  };

  var stream = fs[StreamType](path);

  stream.on('error', erred.bind(stream));
  stream.on('open', opened.bind(stream, null, stream));

  return stream;
};

var createReadStream = createStream.bind(this, 'read');
var createWriteStream = createStream.bind(this, 'write');

var copy = function(from, to, cb){  
  createReadStream(from, cb, function(err, fromStream) {
    createWriteStream(to, cb, function(err, toStream) {
      fromStream.pipe(toStream); 
      fromStream.on('end', cb);
    });
  });
};