spawn and pipe

spawn.js

var spawn = function spawn(cmd, args, callback) {
  var stderr = [], stdout = [],
      ch = child.spawn(cmd, args);

  ch.stdout.pipe(process.stdout, {end: false});
  ch.stderr.pipe(process.stderr);
  ch.stdout.on('data', function(data) { stdout[stdout.length] = data; });
  ch.stderr.on('data', function(data) { stderr[stderr.length] = data; });
  ch.on('exit', (callback || function (code) {
    console.log('done', arguments);
  }));

  return ch;
};