Catching STDERR output

[Jigarius]

I'm not sure if y'all take support requests directly through the issue queue, so I'll try my luck. I created the tool Drall and one of it's main features is parallel processing, which is powered by amphp/process.

Reference: context.

Question 1: Catch STDERR

$sOutput = yield ByteStream\buffer($process->getStdout());

Here, I only get the STDOUT contents from $process. How do I get both STDOUT and STDERR, preferably, intermingled output, i.e. not in separate variables. Is appending 2>&1 the only way? Or is there another way?

Question 2: No buffer

Currently, I use ByteStream\buffer($process->getStdout()); where I catch the output in a variable. Is there a way to let the output go to STDOUT directly instead of catching it in a variable?

Any help will be appreciated.

[Niklas Keller]

You can use Amp\ByteStream\pipe to stream the contents of one stream to another stream. Doing this for both stdout and stderr will likely give you what you're asking for:

async(ByteStream\pipe(...), $process->getStdout(), ByteStream\getStdout())->ignore();
async(ByteStream\pipe(...), $process->getStderr(), ByteStream\getStderr())->ignore();

[Niklas Keller]

If you want both streamed to stdout, you can of course change the destination in the second call.

[Jigarius]

Thanks a ton for the answer. One last question in this regard.

In the given context, how do I break the each?

Loop::run(function () use ($values, $command, $placeholder, $output, $progressBar, $workers, &$exitCode) {
  yield ConcurrentIterator\each(
    Iterator\fromIterable($values),
    new LocalSemaphore($workers),
    function ($value) use ($command, $placeholder, $output, $progressBar, &$exitCode) {
      // TODO: Break the "each".
    }
}

Will it be a Loop::stop(); by any chance?