Handling OS Signals

Signals can be managed using the Deno.signal method. For instance, consider the following code snippet:

console.log("Press Ctrl-C");

for await (const _ of Deno.signal(Deno.Signal.SIGINT)) {

console.log("interrupted!");

Deno.exit();

}

When we press Ctrl+C, it triggers the SIGINT signal, leading to an interruption of the program. The for-await-of loop allows us to monitor this signal, while Deno.Signal.SIGINT represents the SIGINT signal. The program concludes with Deno.exit().

To execute the program, use the command:

deno run --unstable index.ts

Alternatively, the signal handling can be implemented using promises:

console.log("Press Ctrl-C to end the program");

await Deno.signal(Deno.Signal.SIGINT);

console.log("interrupted!");

Deno.exit();

Stopping Signal Monitoring

If you wish to cease monitoring signals, you can invoke the sig.dispose method. Here’s an example:

const sig = Deno.signal(Deno.Signal.SIGINT);

setTimeout(() => {

sig.dispose();

console.log("No longer watching SIGINT signal");

}, 5000);

console.log("Watching SIGINT signals");

for await (const _ of sig) {

console.log("interrupted");

}

In the setTimeout callback, we call sig.dispose to halt the monitoring of the SIGINT signal. The for-await-of loop will stop after five seconds when sig.dispose is executed.

File System Events

Monitoring file system events can be achieved through the Deno.watchFs method. Below is an example:

const watcher = Deno.watchFs(".");

for await (const event of watcher) {

console.log(event);

}

This code observes the current directory, and we can retrieve events from the event object. The output will display events such as creation, modification, and access of files.

You can run this with the following command:

deno run --allow-read index.ts

Module Metadata

To access module metadata, we can utilize the import.meta property. For example:

console.log(import.meta.url);

console.log(Deno.mainModule);

console.log(import.meta.main);

When executed, this may yield output similar to:

file:///home/runner/IntelligentWorthwhileMice/index.ts

file:///home/runner/IntelligentWorthwhileMice/index.ts

true

In this output, both import.meta.url and Deno.mainModule provide the path of the module, while import.meta.main returns true if it is the entry point.