shell redirect in nodejs

redirect.js

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

function run(cmd) {
  var output, out, index = cmd.indexOf('>');
  if (index > -1) {
    output = cmd.substring(index + 1).replace(/(^\s+|\s+$)/g, '');
    cmd = cmd.substring(0, index).split(/\s+/);
  } else {
    cmd = cmd.split(/\s+/);
  }

  if (output) {
    out = fs.openSync(path.resolve(output), 'a');
  }

  spawn(cmd[0], cmd.slice(1), {stdio: [
    process.stdin,
    out ? out : process.stdout,
    process.stderr
  ]});
}

run('echo hello > a.html');