How to replace node.js process with spawned child?

Question

I am building a node.js application and packaging it as a binary (using nexe) and want to update and restart the process if an update is available. When I spawn the new process and exit, I want the new process to take over the terminal but that is not happening. Here's what I am doing (using child_process):

var spawn = require('child_process').spawn;
var child = spawn(process.execPath, process.argv, {
  cwd: process.cwd(),
  env: process.env,
  detached: true,
  stdio: 'inherit'
});
child.unref();
process.exit();

The child process prints all its console logs on the terminal but goes into the background. Where am I going wrong? I am using OS X Mavericks.

Answer 1

You can do something like this:

When you start the application, start it via another script. This will spawn the child process and kill it as needed.

mother.js

var child;
var spawn = require('child_process').spawn;
var argv =  process.argv;
argv.shift();
argv.shift();

function startChild(){
  console.log("STARTING", process.execPath, "child.js", argv);
  child = spawn(process.execPath,  ["child.js", argv], {
    cwd: process.cwd(),
    env: process.env,
    detached: true
  });
  child.on('error', function(e){console.log(e)});
  child.stdout.pipe(process.stdout);
  console.log("STARTED with PID:", child.pid);
}


process.on('SIGQUIT', function() {
  child.kill();
  startChild();
});
startChild();

child.js

(function(){
  console.log("Started child process");
  setInterval(function(){console.log("running")}, 1000);
})();

You can then send ctrl+c to kill the thing. To reload send ctrl+\ or invoke in mother.js from your update function.