gistfile1.js

var eventstream = require('event-stream');
var fs = require('fs');

// creates a new write stream on first write() call
exports.createLazyWriteStream = function(wsFactory) {
  var Stream = require('stream');
  var s = new Stream;
  var ws; 

  s.writable = true;
  s.write = function(buf) {
    if (!ws) {
      console.log('creating ws');
      ws = wsFactory();

      var self = this;
      ws.on('drain', function() { self.emit('drain'); }); 
      ws.on('error', function(err) { self.emit('error', err); }); 
      ws.on('close', function() { self.emit('close'); }); 
      ws.on('pipe', function(src) { self.emit('pipe', src); }); 
    }   
    console.log('> ' + buf);
    return ws.write(buf);
  };  

  s.end = function(buf) {
    if (arguments.length) {
      s.write(buf);
    }   
    s.writable = false;
    if (ws) {
      ws.end();
    }   
  };  

  s.destroy = function () {
    s.writable = false;
    if (ws) {
      ws.destroy();
    }   
  };  

  return s;
};

var s = exports.createLazyWriteStream(function() {
  return fs.createWriteStream('./tmp.data', {flags: 'a'});
});

s.on('close', function() {
  console.log('closed... done');
});

console.log('writing');
setTimeout(function() {
  s.write('oh hai');
}, 5000);

console.log('ending');
s.end();

console.log('done');