Simulating linux terminal in browser

Question

I have read about Fabrice Bellard's linux simulation in browser.

How does Linux emulator in Javascript by Fabrice Bellard work?

Today I stumbled upon this site, where they are simulating full linux terminal in browser, I am able to run python, perl etc. I know they are running their site on node.js, but I couldn't figure out how they exactly simulating the terminal.

http://runnable.com/UWRl3KlLuONCAACG/read-files-from-filesystem-in-python

Answer 1

The full linux is http://docker.io, the rest is https://github.com/Runnable/dockworker

We're not simulating the terminal but as Kyle says, replicating the terminal over websockets (with an ajax fallback).

In the browser we're using https://github.com/chjj/term.js which was derived from Fabrice Bellard's emulator. It handles the output, and also the keystroke capture.

Answer 2

Let me prefix this by saying it is NOT a good idea to do this.

But, You can spawn a shell and use web-sockets or XMLHttpRequests to push keypresses to the spawned server process. Here's a working example of one that runs on windows. Unfortunately, I didn't get around to hooking up / figuring out Ctrl+c. But, you should get the gist of it.

  require("underscore");

  var Server = {},
      express = require("express"),
      path = require("path"),
      sys = require("sys"),
      application_root = __dirname;

  global.Server = Server;
  Server.root = application_root;
  global.app = express();

  Server.setup = require("./lib/setup.js").setup({
    //redis: require("./lib/redis-client").createClient(),
    app: app, 
    //mongoose : require("mongoose"),
    io : require("socket.io"),
    express : express,
    port: 1773,
    paths : {
      views :  path.join(application_root,"app","views"),
      root : path.join(application_root,"public"),
      controllers : path.join(application_root,"app","controllers"),
      models : path.join(application_root,"app","models")
    }
  });

  var proc = require('child_process'),
      cmd;

  app.socket.on('connection', function(socket) {
    if (!cmd) {
      //console.log('spawning cmd');
      cmd = proc.spawn('cmd');

      //console.log(cmd?'CMD started':'CMD not started');

      if (cmd.stdout) {
        //console.log('stdout present');
        cmd.stdout.on('data',function(data) {
          if (data) {
            //console.log("data: "+data);
            socket.emit('cmd', ""+data);
          }
        });
      }
      if (cmd.stderr) {
        cmd.stderr.on('data', function(data) {
          //console.log('stderr present');
          if (data) {
            socket.emit('cmd', ""+data);
          }
        });
      }

      cmd.on('exit', function() {
        //console.log('cmd exited');
        socket.emit('cmd', '[CMD Shutdown]');
        if (cmd) {
          cmd.kill();
          cmd = null;
        }
      });
    }

    socket.on('sendCmd', function(data) {
      if (data && data.buffer) {
        var kB = data.buffer.replace("\r","\n");
        if (cmd && cmd.stdin) {
          cmd.stdin.write(kB);
        }
      }
    });

    socket.on('disconnect', function() {
      console.log('connection closed');
      if (cmd) {
        cmd.stdin.end(); //.kill();
        if (cmd) {
          cmd.kill();
          cmd = null;
        }
      }
    });
  });

Edit: Actually, this is a portion of a working example. It's missing the client side where you capture and send the keystrokes to the server. But, it should give you the general idea.