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: [
"fmt",
"-",
],
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')"));
writer.releaseLock();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://docs.deno.com/examples/scripts/subprocesses_spawn.ts