Handle OS Signals

This program makes use of an unstable Deno feature. Learn more about unstable features.

Concepts

• Use the --unstable flag to access new or unstable features in Deno.
• Deno.signal can be used to capture and monitor OS signals.
• Use the dispose() function of the Deno.signal SignalStream to stop watching the signal.

Async iterator example

You can use Deno.signal() function for handling OS signals:

1. /**
2. * async-iterator-signal.ts
3. */
4. console.log("Press Ctrl-C to trigger a SIGINT signal");
5. for await (const _ of Deno.signal("SIGINT")) {
6. console.log("interrupted!");
7. Deno.exit();
8. }

Run with:

1. deno run --unstable async-iterator-signal.ts

Promise based example

Deno.signal() also works as a promise:

1. /**
2. * promise-signal.ts
3. */
4. console.log("Press Ctrl-C to trigger a SIGINT signal");
5. await Deno.signal("SIGINT");
6. console.log("interrupted!");
7. Deno.exit();

Run with:

1. deno run --unstable promise-signal.ts

Stop watching signals

If you want to stop watching the signal, you can use dispose() method of the signal object:

1. /**
2. * dispose-signal.ts
3. */
4. const sig = Deno.signal("SIGINT");
5. setTimeout(() => {
6. sig.dispose();
7. console.log("No longer watching SIGINT signal");
8. }, 5000);

10. console.log("Watching SIGINT signals");
11. for await (const _ of sig) {
12. console.log("interrupted");
13. }

Run with:

1. deno run --unstable dispose-signal.ts

The above for-await loop exits after 5 seconds when sig.dispose() is called.