Getting command line output dynamically

Question

I'm running a program using command line in c# this program produce some logs while its running in need to display this logs whenever it get change. I wrote the following code but it shows all the logs once the process has been killed and during the running time my program is not responding. how can I fix it?

regards

ProcessStartInfo procStartInfo = new System.Diagnostics.ProcessStartInfo("cmd", "/c " + "C:\\server.py");
Process proc = new Process();
procStartInfo.WindowStyle = ProcessWindowStyle.Hidden;
procStartInfo.UseShellExecute = false;
procStartInfo.RedirectStandardOutput = true;
//procStartInfo.CreateNoWindow = true;
proc.StartInfo = procStartInfo;
proc.Start();
string output = proc.StandardOutput.ReadToEnd();
proc.WaitForExit(300);
LogstextBox.Text = output;

Edited: well, I tried to use OutputDataReceived but it doesn't show any result, here is the changed code:

{
            //processCaller.FileName = @"ping";
            //processCaller.Arguments = "4.2.2.4 -t"; this is working
            processCaller.FileName = @"cmd.exe";
            processCaller.Arguments = "/c c:\\server.py"; //this is not working
            processCaller.StdErrReceived += new DataReceivedHandler(writeStreamInfo);
            processCaller.StdOutReceived += new DataReceivedHandler(writeStreamInfo);
            processCaller.Completed += new EventHandler(processCompletedOrCanceled);
            processCaller.Cancelled += new EventHandler(processCompletedOrCanceled);
            this.richTextBox1.Text = "Server Started.." + Environment.NewLine;
            processCaller.Start();
    }

    private void writeStreamInfo(object sender, DataReceivedEventArgs e)
    {
        this.richTextBox1.AppendText(e.Text + Environment.NewLine);
    }

Answer 1

This is the problem:

string output = proc.StandardOutput.ReadToEnd();

You won't get to the "end" of standard output until the process has terminated.

You should be reading a line at a time - or possibly just subscribing to the OutputDataReceived event (and following the documented other requirements for that event).

EDIT: Here's sample code which works for me:

using System;
using System.Diagnostics;
using System.Threading;

class Program
{
    public static void Main()
    {
        ProcessStartInfo startInfo = new ProcessStartInfo("cmd", "/c " + "type Test.cs")
        {
            WindowStyle = ProcessWindowStyle.Hidden,
            UseShellExecute = false,
            RedirectStandardOutput = true,
            CreateNoWindow = true
        };

        Process process = Process.Start(startInfo);
        process.OutputDataReceived += (sender, e) => Console.WriteLine(e.Data);
        process.BeginOutputReadLine();
        process.WaitForExit();
        // We may not have received all the events yet!
        Thread.Sleep(5000);
    }
}

Note that in your sample code, you're accessing the UI on whatever thread the OutputDataReceived handler is called - that looks like a bad idea to me.

Answer 2

You can use the Process.BeginOutputReadLine Method. The link shows a complete working example in C# which uses the OutputDataReceived event. That code example should do what you want.