Express / node / socket.io code to stream unix child process output over websockets

webtail.js

//
// Just skip to the bottom
//

var express = require('express');
var io = require('socket.io');

var app = module.exports = express.createServer();

// Configuration

app.configure(function(){
  app.set('views', __dirname + '/views');
  app.set('view engine', 'html');
  app.use(express.bodyParser());
  app.use(express.methodOverride());
  app.use(app.router);
  app.use(express.static(__dirname + '/public'));
  app.register('.html', require('ejs'));
});

app.configure('development', function(){
  app.use(express.errorHandler({ dumpExceptions: true, showStack: true })); 
});

app.configure('production', function(){
  app.use(express.errorHandler()); 
});

// Routes

app.get('/', function(req, res){
  res.render('index', {
    title: 'Express'
  });
});

// Only listen on $ node app.js

if (!module.parent) {
  app.listen(3000);
  console.log("Express server listening on port %d", app.address().port);
}

var spawn = require('child_process').spawn;

var socket = io.listen(app, {transports:['websocket']});

socket.on('connection',
          function(client){ 
              client.on('message',
                       function(path) {
                           console.log("I gots a path: " + path);
                           tail_f(path, client);
                       });
          });

var tail_f = function (file, client) {
    var proc = spawn('tail', ['-f', file]);

    proc.stdout.on('data',
        function(data) {
            console.log('file: (' + file + ') ' + data.toString());
            client.send(data.toString());
        });
};