TangJieHao•11mo ago

deno command stdin, stdout continous reading

I am trying to spawn an AI (cpp code) however after launching the code it immediately exits. It also isn't providing any stdout either. relevant code:

async function load_kata_go(config) {
  const command = new Deno.Command(config.EXE, {
    args: ["analysis", "-model", config.MODEL, "-config", config.CONFIG],
    stdin: "piped",
    stdout: "piped",
    stderr: "piped",
  });

  const process = command.spawn();
  return process;
}

async function main() {
  const cli_kata_config = await load_cli_config();
  const katago = await load_kata_go(cli_kata_config);

  const result = await katago.output();
  console.log(new TextDecoder().decode(result.stdout));

  //command args
  //command settings
  //AI
  //analyze games
}

main();

async function load_kata_go(config) {
  const command = new Deno.Command(config.EXE, {
    args: ["analysis", "-model", config.MODEL, "-config", config.CONFIG],
    stdin: "piped",
    stdout: "piped",
    stderr: "piped",
  });

  const process = command.spawn();
  return process;
}

async function main() {
  const cli_kata_config = await load_cli_config();
  const katago = await load_kata_go(cli_kata_config);

  const result = await katago.output();
  console.log(new TextDecoder().decode(result.stdout));

  //command args
  //command settings
  //AI
  //analyze games
}

main();

2 Replies

pyrote•11mo ago

If I replace config.EXE with "echo" the Deno code behaves correctly and prints stdout. Also tried a mock bash script too so the issue seems to be with that exe. Have you tried printing result.stderr to see if the exe is outputting any error messages?

TangJieHaoOP•11mo ago

The issue for me was that the program wasn't persistent and it ended immediately. Even when I hard coded it. I got reading the stream to work.

async function readStream(stream, handler) {
  const reader = stream.getReader();
  try {
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;
      const text = new TextDecoder().decode(value);
      handler(text); 
    }
  } catch (error) {
    console.error('Stream reading error:', error);
  } finally {
    reader.releaseLock();
  }
}

async function readStream(stream, handler) {
  const reader = stream.getReader();
  try {
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;
      const text = new TextDecoder().decode(value);
      handler(text); 
    }
  } catch (error) {
    console.error('Stream reading error:', error);
  } finally {
    reader.releaseLock();
  }
}

And used this:

async function main() {
  const cli_kata_config = await load_cli_config();
  const katago = await load_kata_go(cli_kata_config);

  // Setup continuous reading of stdout and stderr
  readStream(katago.stdout, (text) => console.log('stdout:', text));
  readStream(katago.stderr, (text) => console.error('stderr:', text));

  const analysisRequest = {
    //...
  };
 await gameAnalysis(game, katago)
  await katago.stdin.close();

  const status = await katago.status;
  console.log('Subprocess exited with:', status.code);
}

main().catch(console.error);

async function main() {
  const cli_kata_config = await load_cli_config();
  const katago = await load_kata_go(cli_kata_config);

  // Setup continuous reading of stdout and stderr
  readStream(katago.stdout, (text) => console.log('stdout:', text));
  readStream(katago.stderr, (text) => console.error('stderr:', text));

  const analysisRequest = {
    //...
  };
 await gameAnalysis(game, katago)
  await katago.stdin.close();

  const status = await katago.status;
  console.log('Subprocess exited with:', status.code);
}

main().catch(console.error);

W/e the issue was. Katago doesn't exit immediately