Prevent input/output mixing in Node.js console?

Question

I just managed to to get a Node.js minecraft bot API (called mineflayer) to work. When I was making minecraft bot the last time (in C++, all by myself), I had a problem that when writing in the console, the server messages would mix with whatever I'm writing. The answers I got back then seemed to have too complicated/unclear solutions so I gave up.

Now I was hoping that Node.js has this problem solved, but apparently not. Is there an easy solution in Node.js? What I want is this:

image description

But now, commands that I'm writing mix with output (red is written input, green is console output, colored using GIMP):

image description

I am using the readline module for that:

var readline = require("readline");
var rl = readline.createInterface({
    input: process.stdin,
    output: null,
});

rl.on('line', function(line) {
  var inp = line.trim();
  //Bot internal commands start with ~
  if(line[0]=='~') {
    command(line.substr(1));
  }
  else {
    //use server chat
    bot.chat(line);
  }
});

Just an idea: I guess you could take a whole different approach on that and make a web app instead of a command line interface. You would use Node.js with Express and present a simple page where you can input commands. You could use HTML elements like buttons and other form controls to improve your user interface. To display the output in real time, you could use [socket.io](http://stackoverflow.com/a/24232050/778272). — Lucio Paiva, Jul 11 '15 at 17:52

Lucio Paiva · Answer 1 · 2015-07-11T17:48:14.137

I'm starting with a simple functional example just to show you a way to do it:

var
    readline = require("readline"),
    ansi = require('ansi');

var rl = readline.createInterface({
    input: process.stdin,
    output: null
});

ansi.clear();
ansi.row(1);

rl.on('line', function(line) {

    ansi.row(2);
    ansi.clearLine();
    ansi.print(line);

    ansi.row(1);
    ansi.clearLine();
});

The library ansi is a simple test I've made months ago to manipulate terminal lines using ANSI escape codes. To use it, simply run the following command in the same folder as the code above:

npm install https://github.com/luciopaiva/ansi.git

You can check my code by going directly to my library's repository.

The code is very simple and I recommend that you copy it and adapt to your needs.

ansi.clear() just clears the whole terminal, then ansi.row(1) moves the cursor to the first row, where you will be able to input commands. In my simple example, the code will just print to row #2 what the user typed before hitting the return key. Then just run the code above to see it working and adapt it to a mechanism that rolls the messages along the remaining lines of the terminal.

I suppose that in that case I can no longer use `console.log` without problems... — Tomáš Zato, Jul 11 '15 at 17:10
Yeah, you'd have to make your own custom log() to keep track of line position. — Lucio Paiva, Jul 11 '15 at 17:20
Just have in mind that `console.log` won't work with any other approach that involves manipulating the cursor. If you use libraries like [blessed](https://github.com/chjj/blessed) or TooTallNate's [ansi](https://github.com/TooTallNate/ansi.js/), you'd have to face that problem. Like I said in a comment to your question, a web app is a much better solution to a UI for your bot - certainly a much more elegant approach. — Lucio Paiva, Jul 11 '15 at 18:14

Prevent input/output mixing in Node.js console?

1 Answers1