What is the Windows equivalent of process.on('SIGINT') in node.js?

Question

I'm following the guidance here (listening for SIGINT events) to gracefully shutdown my Windows-8-hosted node.js application in response to Ctrl+C or server shutdown.

But Windows doesn't have SIGINT. I also tried process.on('exit'), but that seems to late to do anything productive.

On Windows, this code gives me: Error: No such module

process.on( 'SIGINT', function() {
  console.log( "\ngracefully shutting down from  SIGINT (Crtl-C)" )
  // wish this worked on Windows
  process.exit( )
})

On Windows, this code runs, but is too late to do anything graceful:

process.on( 'exit', function() {
  console.log( "never see this log message" )
})

Is there a SIGINT equivalent event on Windows?

Answer 1

You have to use the readline module and listen for a SIGINT event:

http://nodejs.org/api/readline.html#readline_event_sigint

if (process.platform === "win32") {
  var rl = require("readline").createInterface({
    input: process.stdin,
    output: process.stdout
  });

  rl.on("SIGINT", function () {
    process.emit("SIGINT");
  });
}

process.on("SIGINT", function () {
  //graceful shutdown
  process.exit();
});

Answer 2

I'm not sure as of when, but on node 8.x and on Windows 10 the original question code simply works now.

process.on( "SIGINT", function() {
  console.log( "\ngracefully shutting down from SIGINT (Crtl-C)" );
  process.exit();
} );

process.on( "exit", function() {
  console.log( "never see this log message" );
} );

setInterval( () => console.log( "tick" ), 2500 );

also works with a windows command prompt.

Answer 3

Unless you need the "readline" import for other tasks, I would suggest importing "readline" once the program has verified that it's running on Windows. Additionally, for those who might be unaware - this works on both Windows 32-bit and Windows 64-bit systems (which will return the keyword "win32"). Thanks for this solution Gabriel.

if (process.platform === 'win32') {
  require('readline')
    .createInterface({
      input: process.stdin,
      output: process.stdout
    })
    .on('SIGINT', function () {
      process.emit('SIGINT');
    });
}

process.on('SIGINT', function () {
  // graceful shutdown
  process.exit();
});

Answer 4

Nowadays it just works on all platforms, including Windows.

The following code logs and then terminates properly on Windows 10:

process.on('SIGINT', () => {
    console.log("Terminating...");
    process.exit(0);
});

Answer 5

Currently there is still no support in node for capturing the windows console control events, so there are no equivalents to the POSIX signals:

https://github.com/joyent/node/issues/1553

However the tty module documentation does give an example of a mechanism to capture the key presses in order to initiate a graceful shutdown, but then this does only work for ctrl+c.

var tty = require('tty');

process.stdin.resume();
tty.setRawMode(true);

process.stdin.on('keypress', function(char, key) {
  if (key && key.ctrl && key.name == 'c') {
    console.log('graceful exit of process %d', process.pid);
    process.exit();
  }
});

Answer 6

Nothing above worked for me, so workaround has been to have a readline hanging and catch the signal from there.

Here my solution:

const readline = require('readline');

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

// Flag to be able to force the shutdown
let isShuttingDown = false;

// https://nodejs.org/api/readline.html
rl.on('SIGINT', async () => {
  if (isShuttingDown) {
    logger.info("Forcing shutdown, bye.");
    process.exit();
  } else {
    if (!<yourIsCleanupNecessaryCheck>()) {
      logger.info("No cleanup necessary, bye.");
      process.exit();
    } else {
      logger.info("Closing all opened pages in three seconds (press Ctrl+C again to quit immediately and keep the pages opened) ...");
      isShuttingDown = true;
      await sleep(3000);
      await <yourCleanupLogic>();
      logger.info("All pages closed, bye.");
      process.exit();
    }
  }

function sleep(ms: number) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

It's quite vanilla, it's asynchronous, and it works both on MacOS 11.3 and Windows 10 (at the time of writing).

Answer 7

Since node.js 0.8 the keypress event no longer exists. There is however an npm package called keypress that reimplements the event.

Install with npm install keypress, then do something like:

// Windows doesn't use POSIX signals
if (process.platform === "win32") {
    const keypress = require("keypress");
    keypress(process.stdin);
    process.stdin.resume();
    process.stdin.setRawMode(true);
    process.stdin.setEncoding("utf8");
    process.stdin.on("keypress", function(char, key) {
        if (key && key.ctrl && key.name == "c") {
            // Behave like a SIGUSR2
            process.emit("SIGUSR2");
        } else if (key && key.ctrl && key.name == "r") {
            // Behave like a SIGHUP
            process.emit("SIGHUP");
        }
    });
}

Answer 8

Windows + Git Bash/Cygwin solution:

None of the other solutions for Windows and Git Bash worked, so my solution was to simply use WINPTY as follows to launch Node:

My package.json has this start script:

"start": "winpty node app.js"

This was inspired by the accepted answer here for similar Python issue:

python error Suppressing signal 18 to win32

Note: WINPTY runs on Windows XP and beyond.