CODEWITHSUNDEEP
c#
Ian
Ian

Reputation: 4909

Process.StandardOutput stream to events

This is really a streams question, but I'm asking specifically to solve my current problem with processes.

System.Diagnostics.Process exposes StandardOutput as a stream. I want to listen to this stream and process its output line by line. Obviously there's no direct correlation between input and output, but let's add the slightly artificial requirement that we can process output "by line".

So most examples of using it look like this:

using (Process process = Process.Start(start))
{
    //
    // Read in all the text from the process with the StreamReader.
    //
    using (StreamReader reader = process.StandardOutput)
    {
    string result = reader.ReadToEnd();
    Console.Write(result);
    }
}

Which is of no use as it isn't event driven and assumes the process lives just long enough to return some output. By event driven, it doesn't have to be an event. A lambda, callback, event, whatever, I just want notification when a whole line is output and I want to be able to shutdown cleanly when I finish with the process.

Essentially I'm asking are streams poll only.

Thanks

Upvotes: 0

Views: 384

Answers (1)

usr
usr

Reputation: 171178

You can receive data using the Process.OutputDataReceived event. It can be tricky to use. Search Stack Overflow for it and you'll find a few synchronization issues and pitfalls.

In general you never need to poll a stream for data. In fact there is no way to poll as far as I'm aware. You either read synchronously or asynchronously. Your call will only complete when there is data or the stream is depleted.

In the async case you can view the callback you receive as an event. So just call BeginReadLine and that's your event. Or do it with tasks.

Upvotes: 1

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