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cli

Handling OS Signals

You can listen for OS signals using the `Deno.addSignalListener` function. This allows you to do things like gracefully shutdown a server when a `SIGINT` signal is received.

console.log("Counting seconds...");

let i = 0;
We isolate the signal handler function so that we can remove it later.
function sigIntHandler() {
  console.log("interrupted! your number was", i);
  Deno.exit();
}
Then, we can listen for the `SIGINT` signal, which is sent when the user presses Ctrl+C.
Deno.addSignalListener("SIGINT", sigIntHandler);
While we're waiting for the signal, we can do other things, like count seconds, or start a server.
const interval = setInterval(() => {
  i++;
}, 1000);
And, after 10 seconds, we can exit and remove the signal listener.
setTimeout(() => {
  clearInterval(interval);
  Deno.removeSignalListener("SIGINT", sigIntHandler);
  console.log("done! it has been 10 seconds");
}, 10_000);

Run this example locally using the Deno CLI:

deno run https://byexample-wwv03xf36j0g.deno.dev/os-signals.ts

Additional resources:

Process InformationEnvironment Variables