Detecting CTRL+C in Node.js

Question

I got this code from a different SO question, but node complained to use process.stdin.setRawMode instead of tty, so I changed it.

Before:

var tty = require("tty");

process.openStdin().on("keypress", function(chunk, key) {
  if(key && key.name === "c" && key.ctrl) {
    console.log("bye bye");
    process.exit();
  }
});

tty.setRawMode(true);

After:

process.stdin.setRawMode(true);
process.stdin.on("keypress", function(chunk, key) {
  if(key && key.name === "c" && key.ctrl) {
    console.log("bye bye");
    process.exit();
  }
});

In any case, it's just creating a totally nonresponsive node process that does nothing, with the first complaining about tty, then throwing an error, and the second just doing nothing and disabling Node's native CTRL+C handler, so it doesn't even quit node when I press it. How can I successfully handle Ctrl+C in Windows?

salezica · Accepted Answer · 2017-11-10 02:23:59Z

283

If you're trying to catch the interrupt signal SIGINT, you don't need to read from the keyboard. The process object of nodejs exposes an interrupt event:

process.on('SIGINT', function() {
    console.log("Caught interrupt signal");

    if (i_should_exit)
        process.exit();
});

Edit: doesn't work on Windows without a workaround. See here

edited Nov 10, 2017 at 2:23

user6269864

answered Nov 23, 2013 at 17:38

salezica

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2 Comments

Griffork Over a year ago

For future readers, this question is answered for windows here: stackoverflow.com/a/14861513/2020425

crxyz Over a year ago

The windows problem is already fixed

asciidude · Accepted Answer · 2022-03-20 03:34:31Z

The NPM module, death, uses SIGINT, SIGQUIT, and SIGTERM.

So basically, all you need to do is:

process.on('SIGINT', () => {});  // CTRL+C
process.on('SIGQUIT', () => {}); // Keyboard quit
process.on('SIGTERM', () => {}); // `kill` command

As a side note, this may actually call SIGINT, SIGQUIT, and SIGTERM numerous times... not sure why, it did for me.

I fixed it by doing this:

let callAmount = 0;
process.on('SIGINT', function() {
    if(callAmount < 1) {
        send.success(`✅ The server has been stopped`, 'Shutdown information', 'This shutdown was initiated by CTRL+C.');
        setTimeout(() => process.exit(0), 1000);
    }

    callAmount++;
});

If all you want to do is detect the interruption keys, just use SIGINT

Edit: I didn't realize this post was very old, oh well, it's helpful to others I guess!

Mwiza · Accepted Answer · 2017-10-01 19:23:05Z

8

For those who need the functionality, I found death (npm nodule, hah!).

Author also claims it works on windows:

It's only been tested on POSIX compatible systems. Here's a nice discussion on Windows signals, apparently, this has been fixed/mapped.

I can confirm CTRL+C works on win32 (yes, I am surprised).

edited Oct 1, 2017 at 19:23

Mwiza

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answered Jul 20, 2015 at 21:52

honzajde

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Comments

chovy · Accepted Answer · 2023-02-18 10:33:15Z

-3

process.on('signal', async (signal) => {
    console.log('signal: ', signal);
    if (signal === 'SIGINT') {
        console.log('Received SIGINT. Calling save function...');
        await amazon.saveData();
    }

    process.exit(0);
});

answered Feb 18, 2023 at 10:33

chovy

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1 Comment

Tyler2P Over a year ago

Your answer could be improved by adding more information on what the code does and how it helps the OP.

ThatNerdEvan · Accepted Answer · 2022-04-28 15:13:37Z

-8

if (event.key == "ctrl+c") {
    console.log("goodbye");
    break;
}

edited Apr 28, 2022 at 15:13

user17242583

answered Apr 28, 2022 at 15:11

ThatNerdEvan

1

2 Comments

user17242583 Over a year ago

This won't work. event.key isn't for key combinations, so it will never be anything like ctrl+c.

Viradex Over a year ago

break only works in for and while loops. Running it in an if statement will cause Node.js to crash. Use process.exit() instead.

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