Console application doesn't periodically flush output

Question

I'm using a 3rd party console application that periodically outputs data to the console line by line. When I attempted to run it through my App so that I can parse the output data, I noticed that the OutPutstream was readable only AFTER the application quits.

I tested my application with a C# console application that outputs something to the console every 5 seconds and it's working as expected. The 3rd party process I'm calling is either written in Java or C++ (not sure), but it seems that it might not adhere to the standards that .NET expects of console applications.

Is there another way to read the data output by a console application?

Edit: I'm calling the process from a WPF application. So async reads are required.

Edit 2: The console application reads data from a USB device (an accelerometer - http://www.gcdataconcepts.com/).

Below is the code I used:

    public void RunProcess()
    {
        Process process = new Process();
        process.StartInfo.FileName = "consoleApp.exe";

        process.StartInfo.UseShellExecute = false;
        process.StartInfo.RedirectStandardOutput = true;
        process.StartInfo.CreateNoWindow = true;
        process.OutputDataReceived += new DataReceivedEventHandler(OutputHandler);
        process.Start();
        process.BeginOutputReadLine();
    }

    private void OutputHandler(object sendingProcess, DataReceivedEventArgs outLine)
    {
        if (!string.IsNullOrEmpty(outLine.Data))
        {
            Dispatcher.Invoke(new Action(() =>
            {
                textBlock1.Text += outLine.Data + Environment.NewLine;
            }), System.Windows.Threading.DispatcherPriority.Normal);
        }
    }

I have made a fix for this, you can find it on this similar question... http://stackoverflow.com/a/11675360/361464 — Dean North, Jul 26 '12 at 16:28

score 1 · Answer 1 · edited Jun 25 '12 at 18:35

protected virtual void StartProcess() {
        // Start a new process for the cmd
        process = new Process();
        process.StartInfo.UseShellExecute = false;
        process.StartInfo.RedirectStandardOutput = true;
        process.StartInfo.RedirectStandardError = true;
        process.StartInfo.CreateNoWindow = true;
        process.StartInfo.FileName = FileName;
        process.StartInfo.Arguments = Arguments;
        process.StartInfo.WorkingDirectory = WorkingDirectory;
        process.Start();

        // Invoke stdOut and stdErr readers - each
        // has its own thread to guarantee that they aren't
        // blocked by, or cause a block to, the actual
        // process running (or the gui).
        new MethodInvoker(ReadStdOut).BeginInvoke(null, null);
        new MethodInvoker(ReadStdErr).BeginInvoke(null, null);

    }

    /// <summary>
    /// Handles reading of stdout and firing an event for
    /// every line read
    /// </summary>
    protected virtual void ReadStdOut() {
        string str;
        while ((str = process.StandardOutput.ReadLine()) != null)
        {
            FireAsync(StdOutReceived, this, new DataReceivedEventArgs(str));
        }
    }

    /// <summary>
    /// Handles reading of stdErr
    /// </summary>
    protected virtual void ReadStdErr() {
        string str;
        while ((str = process.StandardError.ReadLine()) != null)
        {
            FireAsync(StdErrReceived, this, new DataReceivedEventArgs(str));
        }
    }

score 0 · Answer 2 · answered Feb 06 '11 at 21:53

0

You can also do it like this:

public void RunProcess()
{
    Process process = new Process();
    process.StartInfo.FileName = "consoleApp.exe";

    process.StartInfo.UseShellExecute = false;
    process.StartInfo.RedirectStandardOutput = true;
    process.StartInfo.CreateNoWindow = true;
    process.Start();

    for (; ; )
    {
        string line = process.StandardOutput.ReadLine();
        if (line == null)
            break;

        Dispatcher.Invoke(new Action(() =>
            {
                textBlock1.Text += outLine.Data + Environment.NewLine;
            }), System.Windows.Threading.DispatcherPriority.Normal);
    }
    ...
}

answered Feb 06 '11 at 21:53

Simon Mourier

132,049
21
248
298

Not working. Same behavior. I only see output when I set `CreateNoWindow = false` and manually close the window. – Omar Feb 08 '11 at 01:19
@Omar - What do you mean "I only see output when...". With this kind of code, you should not see output, that"s the way it should work, because it's redirected. Or do I miss something? – Simon Mourier Feb 08 '11 at 07:16
I meant I can only see the output from the console that I spawned and not in my application which created the process. – Omar Feb 09 '11 at 01:33

score 0 · Answer 3 · answered Feb 06 '11 at 22:03

0

A simpler way would be to use StandardOutput object on your process object. Example code:

Process process = new Process();
process.StartInfo.FileName = @"StackOverflowTest.exe";

process.StartInfo.UseShellExecute = false;
process.StartInfo.RedirectStandardOutput = true;
process.StartInfo.CreateNoWindow = true;
process.Start();

while (!process.StandardOutput.EndOfStream) 
{
    Console.WriteLine("got: " + process.StandardOutput.ReadLine());
}

answered Feb 06 '11 at 22:03

Imre Pühvel

4,468
1
34
49

Not working. Same behavior. I only see output when I set `CreateNoWindow = false` and manually close the window. – Omar Feb 08 '11 at 01:18

Console application doesn't periodically flush output

3 Answers3