Bogus Underground Read-Print-Loop

(A REPL library with some better ergonomics)

As a long time user of Cisco network products and routing daemons such as Quagga (nee Zebra), I've come to enjoy their sort of CLI. The tab completion is really good for exploring what the system can do. Either that or I have Stockholm syndrome setting in and it's actually terrible. I'm never sure when it comes to old command line technologies. I do use plain vi and mksh. So take it with a grain of salt.

The long and short of it is that the command language looks something like this:

show ip routes
show ipv6 routes
show status
enable

and if you press the tab key at a prompt, it'll helpfully spit out what you can do from there for each word, and it also lets you abbreviate if you're not ambiguous.

sh ip r

That's actually a legit alias for show ip routes given that list of available commands.

This package is a client and server for these interactions. There's a generic burpl command, modelled after Quagga's vtysh, and a server component that lets you supply an object of "command": async function pairs, and get back a server you just need to listen on an AF_UNIX socket.

Example

const burpl = require('burpl')
const { promisify } = require('util')
const listen = promisify(require('unix-listen'))

const users = [ "aphrodite", "eris", "persephone", "sappho"];

const server = burpl({
    "help": async () => "There is no help for you",
    "user list": () => users.join("\n"),
    "user add USER": (user) => {
		return `added user '${user}' (I lie)`;
	},
    "user add USER really": async (user) => {
		await Promise.resolve(user).then(user => users.push(user));
		return `added user '${user}' for real`;
	},
})

listen(server, 'test.sock')

You can communicate with this server using burpl -s test.sock.