http://stormy-sunset-78.heroku.com/

heroku-node-test-fs.js

var sys = require('sys'),
    http = require('http'),
    fs = require('fs');

var FILENAME = 'message.txt';

fs.writeFile(FILENAME, 'Hello Node', function (err) {
  if (err) throw err;
  console.log('It\'s saved!');
});

http.createServer(function (request, response) {
  response.writeHead(200, {'Content-Type': 'text/plain'});
  response.end(fs.readFileSync(FILENAME));
}).listen(process.env.PORT || 8000);