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Subprocesses: Spawning


For more complex usecases, we don't simply want the output of some command. In this case, we can spawn a subprocess and interact with it.

The Deno namespace has a unified api for interacting with the outside system called Deno.Command. With it, we can initialize some information about the command but it will not be executed immediately.
const command = new Deno.Command("deno", {
  args: [
  stdin: "piped",
  stdout: "piped",
In a slightly more complex case, we want to interact with a spawned process. To do this, we first need to spawn it.
const process = command.spawn();
We can now pipe the input into stdin. To do this we must first get a writer from the stream and write to it
const writer = process.stdin.getWriter();
writer.write(new TextEncoder().encode("console.log('hello')"));
We must then close stdin
await process.stdin.close();
We can now wait for the process to output the results
const result = await process.output();
console.log(new TextDecoder().decode(result.stdout));

Run this example locally using the Deno CLI:

deno run --allow-run https://examples.deno.land/subprocesses-spawn.ts

Additional resources: