Not able to send commands to cmd.exe process

Question

I am trying to send commands to an open cmd.exe process using StandardInput.WriteLine(str), however none of the commands seem to be sent. First I open a process, with a global variable p (Process p).

p = new Process()
{
    StartInfo = {
        CreateNoWindow = true,
        UseShellExecute = false,
        RedirectStandardError = true,
        RedirectStandardInput = true,
        RedirectStandardOutput = true,
        FileName = @"cmd.exe",
        Arguments = "/C" //blank arguments
    }
};

p.Start();
p.WaitForExit();

After, I try to send a command using a simple method, that logs the result in a text box.

private void runcmd(string command)
{
    p.StandardInput.WriteLine(command);
    var output = p.StandardOutput.ReadToEnd();
    TextBox1.Text = output;
}

Right now I am testing it with DIR, but var output shows up as null, which results in no output. Is there a better way to send a command to the open cmd.exe process?

Answer 1

I could never get it to work with synchronous reads of stdout without closing stdin, but it does work with async reading for stdout/stderr. No need to pass in /c, you only do that when passing in a command through the arguments; you are not doing this though, you are sending the command directly to the input.

var p = new Process()
{
    StartInfo = {
    CreateNoWindow = false,
    UseShellExecute = false,
    RedirectStandardError = true,
    RedirectStandardInput = true,
    RedirectStandardOutput = true,
    FileName = @"cmd.exe"}
};
p.OutputDataReceived += (sender, args1) => Console.WriteLine(args1.Data);
p.ErrorDataReceived += (sender, args1) => Console.WriteLine(args1.Data);
p.Start();
p.BeginOutputReadLine();
p.StandardInput.WriteLine("dir");
p.StandardInput.WriteLine("cd e:");
p.WaitForExit();

Console.WriteLine("Done");