How to handle "press enter to continue" to exit a program when running it from code?

Question

I'm trying to run an external binary from a C# code using the ProcessEx.RunAsync command. However, this binary doesn't have a quiet mode and whenever it's done operating, it prompts "press enter to continue" in order to exit the program. How do I handle this so I won't get a timeout return?

Answer 1

The functionality you describe is similar to what expect tool provides in *nix world.

The program automates interactions with programs that expose a text terminal interface.

There are various options available for you to use and if you are interested in using an existing C# library then the dotnetexpect might solve it for you; note it is quite old.

If you are looking for all hand-coding, here is a PoC to explain the concept. As usual: don't use as-is this is just to demonstrate the concept.

namespace ToExpectOrNotToExpect
{
    class Program
    {
        static void RunAndManage(string command,string args)
        {
            Process processHandle = new Process();
            processHandle.StartInfo.FileName = command;
            processHandle.StartInfo.Arguments = args;
            processHandle.StartInfo.UseShellExecute = false;
            processHandle.StartInfo.RedirectStandardOutput = true;
            processHandle.StartInfo.RedirectStandardInput = true;
            processHandle.StartInfo.CreateNoWindow = false;
            processHandle.Start();


            string data = "";
            while (!processHandle.StandardOutput.EndOfStream)
            {
                // Cheap and cheeky buffer: improve
                char[] buffer = new char[256];
                int n = processHandle.StandardOutput.Read(buffer, 0, 100);
                data += new string(buffer, 0, n);
                Console.WriteLine("GOT: [[ " + data + "]]");
                if (data.IndexOf("Press any key") >= 0)
                {
                    processHandle.StandardInput.Write('\r');
                    // Keeping it simple and exiting for the PoC: improve this in your implementation
                    break;
                }
            }
        }

        static void Main(string[] args)
        {
            RunAndManage("cmd.exe", " /c echo This was fun && echo Really && echo Really && pause && echo Wowzer Pause Bypassed 1>&2 ");
        }
    }
}

Output would look something like this (notice that we sent CarriageReturn once we saw the pause text being emitted):

Detailed and expansive examples are plenty on this idea on Stackoverflow and elsewhere. Here is one.