How do you create a terminal instance within a NodeJS child process?

Question

I am setting up a discord channel to function as an SSH terminal. A NodeJS server will provide the connection. A custom command will spawn a new terminal instance, which can then be used as a shell.

I don't know how to spawn a terminal within a child process. I have tried using the screen and bash commands to no avail.

I am using CentOS 7.

// Code For Discord
var $discord = {
    currentInterface: null,
    send: (data) => {
        /* some code that sends data to a discord channel */
    },
    receive: (data) => {

        // Send Data To Terminal
        if ($discord.currentInterface) {
            $discord.currentInterface.send(data);
        } else {
            $discord.send('**Error:** Terminal has not been spawned.');
        }
    },
    command: (name, args) => {

        // Recieve Discord Commands
        switch (name) {
            case 'spawn':
                $discord.currentInterface = $interface();
            break;
        }
    }
};

// Create Interface
var $interface = function () {

    // Define object
    let x = {
        terminal: child_process.spawn('screen'),
        send: (data) => {

            // Send Input to Terminal
            x.process.stdin.write(data + '\n');
        },
        receive: (data) => {

            // Send Output to Discord
            $discord.send(data);
        }
    };

    // Process Output
    x.terminal.on('stdout', (data) => {
        x.receive(data);
    });

    // Process Errors
    x.terminal.on('stderr', (error) => {
        x.receive(`**Error:**\n${error}`);
    });

    // Return
    return x;
};

The problem lies with creating the terminal itself. How do you create an SSH-style shell within a child process?

Welcome to SO! This is nitpicky but towards the end of your mock-up you have a typo within your last `x.terminal.on` callback. It should be `x.receive(\`**Error:**\n${error}\`);`. — GenericUser, Jan 14 '19 at 17:16
There seems to be a few obstacles here, such as different operating systems and what shell is available. Unless you just want a linux solution for a given shell. — GenericUser, Jan 14 '19 at 17:19
Well, this is for anyone to get an SSH right? Are all users on CentOS 7? Unless I misunderstand the use case here. — GenericUser, Jan 14 '19 at 17:28
I just want to use a discord channel as an SSH terminal. That's the use case. — spacefluff432, Jan 14 '19 at 17:30

score 1 · Answer 1 · answered Jan 14 '19 at 19:56

After realizing how much of an idiot I really am, I found a solution...

// Import Modules
const fs = require('fs');
const child_process = require('child_process');

// Create Interface
var interface = {
    terminal: child_process.spawn('/bin/sh'),
    handler: console.log,
    send: (data) => {
        interface.terminal.stdin.write(data + '\n');
    },
    cwd: () => {
        let cwd = fs.readlinkSync('/proc/' + interface.terminal.pid + '/cwd');
        interface.handler({ type: 'cwd', data: cwd });
    }
};

// Handle Data
interface.terminal.stdout.on('data', (buffer) => {
    interface.handler({ type: 'data', data: buffer });
});

// Handle Error
interface.terminal.stderr.on('data', (buffer) => {
    interface.handler({ type: 'error', data: buffer });
});

// Handle Closure
interface.terminal.on('close', () => {
    interface.handler({ type: 'closure', data: null });
});

Usage...

interface.handler = (output) => {
    let data = '';
    if (output.data) data += ': ' + output.data.toString();
    console.log(output.type + data);
};

interface.send('echo Hello World!');
// Returns: data: Hello World!

interface.send('cd /home');
interface.cwd();
// Returns: cwd: /home

interface.send('abcdef');
// Returns: error: bin/sh: line 2: abcdef: command not found

interface.send('exit');
// Returns: exit

GenericUser · Answer 2 · 2019-01-14T18:05:11.560

0

I'd take a look at the documentation for child_process.execFile. There's an option to set the shell on, but it's disabled by default.

There's also this approach if you want to try setting up a batch script. This is set up for windows and the answer isn't set up for passing arguments, but you should be able to adapt it fairly easily.

edited Jan 14 '19 at 18:05

answered Jan 14 '19 at 17:55

GenericUser

3,003
1
11
17

How do you create a terminal instance within a NodeJS child process?

2 Answers2