How to spawn child process and communicate with it Deno?

Question

Suppose I have 2 script, father.ts and child.ts, how do I spawn child.ts from father.ts and periodically send message from father.ts to child.ts ?

Didier

Answer 1

You have to use the Worker API

father.ts

const worker = new Worker("./child.ts", { type: "module", deno: true });
worker.postMessage({ filename: "./log.txt" });

child.ts

self.onmessage = async (e) => {
  const { filename } = e.data;
  const text = await Deno.readTextFile(filename);
  console.log(text);
  self.close();
};

You can send messages using .postMessage

Hyohyoid

But child process in node allows you to run terminal commands. Seems like the does not – Inhabitancy

You can use Deno.run if you want to spawn shell commands. – Hyohyoid

#61711287 see my answer there – Hyohyoid

Very helpful, thank you. Am I able to send multiple commands and receive multiple responses for the same running process in Deno? I'm having a hard time finding examples. – Inhabitancy

In one of my examples I show how to write to stdin. You need to read from stdout and write to stdin. – Hyohyoid

why is it called 'worker'? – Pretend

Because Deno tries to implement Web APIs when it makes sense, they didn't create the name developer.mozilla.org/en-US/docs/Web/API/Worker/Worker – Hyohyoid

Answer 2

You can use child processes. Here is an example: proc with PushIterable

This will let you send and receive multiple commands from non-Deno child processes asynchronously, as well as Deno child processes.

Be careful as this requires --allow-run to work, and this almost always breaks out of the sandbox, if you care about that.

Mclaughlin