Question

I can run a command line process using process.start().
I can provide input using standard input. After that when the process demands user input again, how can my program know and pass the input to that exe?

Answer 1

There’s an example here that sounds similar to what you need, using Process.StandardInput and a StreamWriter.

        Process sortProcess;
        sortProcess = new Process();
        sortProcess.StartInfo.FileName = "Sort.exe";

        // Set UseShellExecute to false for redirection.
        sortProcess.StartInfo.UseShellExecute = false;

        // Redirect the standard output of the sort command.  
        // This stream is read asynchronously using an event handler.
        sortProcess.StartInfo.RedirectStandardOutput = true;
        sortOutput = new StringBuilder("");

        // Set our event handler to asynchronously read the sort output.
        sortProcess.OutputDataReceived += new DataReceivedEventHandler(SortOutputHandler);

        // Redirect standard input as well.  This stream
        // is used synchronously.
        sortProcess.StartInfo.RedirectStandardInput = true;
        sortProcess.Start();

        // Use a stream writer to synchronously write the sort input.
        StreamWriter sortStreamWriter = sortProcess.StandardInput;

        // Start the asynchronous read of the sort output stream.
        sortProcess.BeginOutputReadLine();
        Console.WriteLine("Ready to sort up to 50 lines of text");
        String inputText;
        int numInputLines = 0;
        do 
        {
            Console.WriteLine("Enter a text line (or press the Enter key to stop):");

            inputText = Console.ReadLine();
            if (!String.IsNullOrEmpty(inputText))
            {
                numInputLines ++;
                sortStreamWriter.WriteLine(inputText);
            }
        }

hope that helps