how can i read the output from C# process before the process end?

Question

i want to create IDE for python that can run line by line like anaconda. so i want return the output after each python command .

Edit: the solution is:

public Process cmd = new Process();
public  string output = "";
{
cmd.StartInfo.FileName = "python.exe";
cmd.StartInfo.Arguments = @"-i";//this was the problem
cmd.StartInfo.RedirectStandardInput = true;
cmd.StartInfo.RedirectStandardOutput = true;
cmd.StartInfo.UseShellExecute = false;

cmd.OutputDataReceived += new DataReceivedEventHandler((sender2, e2) =>
{
    if (!String.IsNullOrEmpty(e2.Data))
    {
        output += e2.Data.ToString()+"\n";

    }
});
cmd.Start();
cmd.BeginOutputReadLine();
}

{
cmd.StandardInput.WriteLine(result);//the output will take some time to complete
}

https://unix.stackexchange.com/questions/182537/write-python-stdout-to-file-immediately — Hans Passant, Oct 05 '20 at 11:12

audzzy · Accepted Answer · 2020-10-05T12:20:07.330

-1

register to the OutputDataReceived event to get data :

    cmd.OutputDataReceived += new DataReceivedEventHandler((sender, e) =>
    {
        if (!String.IsNullOrEmpty(e.Data))
        {
            // do what you need with the output (for instance append output)
        }
    });

and after cmd.Start() add:

   cmd.BeginOutputReadLine();

this causes the process to read the redirected output..

so the final code would be:

        Process cmd = new Process();
        cmd.StartInfo.FileName = @"python.exe";
        cmd.StartInfo.Arguments = @"-i";
        cmd.StartInfo.RedirectStandardOutput = true;
        cmd.StartInfo.RedirectStandardInput = true;
        cmd.StartInfo.UseShellExecute = false;
        cmd.OutputDataReceived += new DataReceivedEventHandler((sender, e) =>
        {
            if (!String.IsNullOrEmpty(e.Data))
            {
                // do what you need with the output (for instance append output)
                cmd.StandardInput.WriteLine("python comand 1");
                cmd.StandardInput.WriteLine("python comand 2");
                cmd.StandardInput.WriteLine("another comand 3");

            }
        });
        cmd.Start();
        cmd.BeginOutputReadLine();

the exe I'm running basically has a button that on click writes a line to the console, and then reads 3 lines, so the event gets data "my output", and bla1,bla2 and bla3 get the values I wrote to the input:

    private void button1_Click(object sender, EventArgs e)
    {
        Console.WriteLine("my output");
        string bla = Console.ReadLine();
        string bla2 = Console.ReadLine();
        string bla3 = Console.ReadLine();
    }

edited Oct 05 '20 at 12:20

answered Oct 05 '20 at 09:47

audzzy

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more details please , i have tried this solution and it didn't work. – Osama Adel Oct 05 '20 at 09:56
there was another line missing, I edited the answer – audzzy Oct 05 '20 at 10:17
i retry this and it didn't work. i have edited the question to your answer. – Osama Adel Oct 05 '20 at 10:49
can you upload your project ? i tried what you said and there is no output. i should close the process so that the output appear. – Osama Adel Oct 05 '20 at 11:13
edited to show what's going on in the exe I'm running.. right now do you have a problem with the input \ output or both? – audzzy Oct 05 '20 at 11:19
i have a problem in the output only. specifically when i want to see the output before the process closed. when the process closed i can easily return all the outputs. but i don't want that. – Osama Adel Oct 05 '20 at 11:25
just realized you're running python code - added a line to set argument - try that – audzzy Oct 05 '20 at 11:39
yes i try to create somthing like anaconda that run a cell of code at a time and see the output from it.. you want me to try what ?? – Osama Adel Oct 05 '20 at 11:45
cmd.StartInfo.Arguments = @"-u"; – audzzy Oct 05 '20 at 11:47
please upload the project. i didn't understand the edited code. – Osama Adel Oct 05 '20 at 12:04
in the c# code, I just added the third line, that sets an argument for the process. "-u" forces the stdout and stderr streams to be unbuffered; – audzzy Oct 05 '20 at 12:05
wooow i finally works . thanks alot. – Osama Adel Oct 05 '20 at 12:13
cmd.StartInfo.Arguments = @"-i"; not u – Osama Adel Oct 05 '20 at 12:14

how can i read the output from C# process before the process end?

1 Answers1