electron/spec/fixtures/api/relaunch/main.js

const { app } = require('electron');
const net = require('net');

const socketPath = process.platform === 'win32' ? '\\\\.\\pipe\\electron-app-relaunch' : '/tmp/electron-app-relaunch';

process.on('uncaughtException', () => {
  app.exit(1);
});

app.whenReady().then(() => {
  const lastArg = process.argv[process.argv.length - 1];
  const client = net.connect(socketPath);
  client.once('connect', () => {
    client.end(String(lastArg === '--second'));
  });
  client.once('end', () => {
    app.exit(0);
  });

  if (lastArg !== '--second') {
    app.relaunch({ args: process.argv.slice(1).concat('--second') });
  }
});