missing x,y for current cursor position on process.stdout

[coolaj86]

I'm a very experienced node.js developer, but not very experienced ANSI terminal developer.

How do I determine the current location of the cursor?

I see that I can determine the window size with process.stdout.columns, process.stdout.rows, and there's a nifty resize event. Awesome.

But there isn't a process.stdout.column and process.stdout.row or process.stdeout.x, process.stdeout.y to tell me where I currently am, which kind of stinks.

Is there a technical reason as to why this isn't available? Or is it just not documented? Or does it need some love and a pull request?

Practical Use Case

I've got a websocket checking on some stuff in the background. Every few seconds it updates a status message in known location the upper right corner. The function should check to see where the cursor is, make the update, and put the cursor back where it was.

[bnoordhuis]

https://gist.github.com/lancejpollard/3765464 is an example of how you can query the tty for the cursor position. The key part is the '\x1b[6n' scan code.

I think the reason node.js doesn't support it natively is that it's not very portable.

[maltekosian]

Why this issue is closed? sh scripts do not work on windows and it is not a build-in method of node.

[gibfahn]

I think the reason node.js doesn't support it natively is that it's not very portable.

As Ben said:

I think the reason node.js doesn't support it natively is that it's not very portable.

Not sure if there is a way to do it in Windows, cc/ @nodejs/platform-windows

[joaocgreis]

https://www.npmjs.com/package/get-cursor-position has Windows support.

[alshdavid]

Is this available in nodejs yet?

[UnluckyNinja]

In case someone come across this issue like me:
Just like bnoordhuis pointed out, write \x1b[6n (or \u001b[6n) to stdout will have the cursor position returned in stdin. And it's doable with only js.

There are js examples on stackoverflow:
https://stackoverflow.com/questions/70033207/how-do-i-get-the-current-cursor-position-relative-to-the-output-with-nodejs-read
Tested in win10 with cmd, powershell 5.1 & 7.4.7 in Windows Terminal. All of them can return cursor position with \x1b[6n.

The only problem I currently have is that when using it with createInterface from node:readline, if the input buffer is long enough (>= 4 chars on my machine), an additional 'R' will be appended to current cursor position.

(EDIT: turns out when the cursor is at column >=10 the input sequence received by keypress event is {"sequence":"\u001b[27;10","name":"undefined","ctrl":false,"meta":false,"shift":false,"code":"[27;10"} where the "R" at the sequence's end is left out.)
(EDIT2: I think I found the cause, it's simply that in the code it doesn't take such sequence into account. It only parse 2 more characters after ";" (1 digit and 1 any char): https://github.com/nodejs/node/blob/3861eccc05751eea2a0915316c16b86caea531ba/lib/internal/readline/utils.js#L182-L188)

And a reproduction, modified from above.

import * as readline from 'node:readline';

const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
const getCursorPos = () => new Promise((resolve) => {
  const termcodes = { cursorGetPosition: '\u001b[6n' };

  process.stdin.setEncoding('utf8');
  process.stdin.setRawMode(true);

  const readfx = function () {
      const buf = process.stdin.read();
      const str = JSON.stringify(buf); // "\u001b[9;1R"
      const regex = /\[(.*)/g;
      const xy = regex.exec(str)[0].replace(/\[|R"/g, '').split(';');
      const pos = { rows: xy[0], cols: xy[1] };
      process.stdin.setRawMode(false);
      resolve(pos);
  }

  process.stdin.once('readable', readfx);
  process.stdout.write(termcodes.cursorGetPosition);
})

const AppMain = async function () {
  process.stdout.write('HELLO');
  const pos = await getCursorPos();
  process.stdout.write("\n");
  console.log({ pos });
  process.stdin.unref()
}

console.log('Type some text >= 4 chars')
setTimeout(()=>{
  setImmediate(AppMain);
}, 2000)

It would be convenient if we can have a builtin function that provides such feature and avoid conflicts/mistakes with readline or any custom interactive console.