run.js

function run(cmd, args, callback) {
  var child = spawn(command, args);
  var stdout = stderr = "";

  child.stdout.setEncoding('utf8');
  child.stdout.addListener("data", function (chunk) { stdout += chunk; });

  child.stderr.setEncoding('utf8');
  child.stderr.addListener("data", function (chunk) { stderr += chunk; });
 
  child.addListener("exit", function (code) {
    if (code == 0) {
      if (callback) callback(null, stdout, stderr);
    } else {
      var e = new Error("Command failed: " + stderr);
      e.code = code;
      if (callback) callback(e, stdout, stderr);
    }
  });
};