I would like to control a few web sites using a UI to start and stop them, changing the ports that the different web server's listen to.

PM2 is a command line utility to manage node sites, but does not have a user interface that I can supply my customer.

How can I run a node.js web site from within another node.js web application.

The following node.js code does not seem to do the work.

```
const { exec } = require('child_process');

....

exec('node app.js', (err, stdout, stderr) => {
    if (err) {
        console.log(`err: ${err}`);
        return;
    }

    // the *entire* stdout and stderr (buffered)
    console.log(`stdout: ${stdout}`);
    console.log(`stderr: ${stderr}`);
});

```

note: regular linux commands instead of the 'node app.js' command work as expected.