Redirect input and output for cmd.exe

Question

I wanna redirect cmd.exe output somewhere, below code works when the command is a line:

Process p = new Process()
{
    StartInfo = new ProcessStartInfo("cmd")
    {
       UseShellExecute = false,
       RedirectStandardInput = true,
       RedirectStandardOutput = true,
       CreateNoWindow = true,
       Arguments = String.Format("/c \"{0}\"", command),
    }
};
p.OutputDataReceived += (s, e) => Messagebox.Show(e.Data);
p.Start();
p.BeginOutputReadLine();
p.WaitForExit();

But how about a series commands like WriteLine():

p.StandardInput.WriteLine("cd...");
p.StandardInput.WriteLine("dir");

how to get output in this situation?

clarify: do you want all outputs of your commands? or just the last one? Calling RunWithRedirect() consecutively already achieves your goal. — Raptor
– Raptor, Commented Apr 8, 2013 at 2:54
while, my commands are in series. Sth like "cd path" and then "do sth", i want all the outputs — L_G
– L_G, Commented Apr 8, 2013 at 3:01
how about Calling RunWithRedirect() consecutively ? sounds no problem in your case. — Raptor
– Raptor, Commented Apr 8, 2013 at 3:12

SHSE · Accepted Answer · 2013-04-08 04:42:09Z

To achieve such behavior you should use /k switch to run cmd.exe in interactive mode.

The problem is to separate inputs from different commands. To do this you could change the standard prompt using prompt command:

prompt --Prompt_C2BCE8F8E2C24403A71CA4B7F7521F5B_F659E9F3F8574A72BE92206596C423D5

So now it is pretty easy to determine the end of command output.

Here is the complete code:

public static IEnumerable<string> RunCommands(params string[] commands) {
    var process = new Process {
        StartInfo = new ProcessStartInfo("cmd") {
            UseShellExecute = false,
            RedirectStandardInput = true,
            RedirectStandardOutput = true,
            CreateNoWindow = true,
            Arguments = "/k",
        }
    };

    process.Start();

    const string prompt = "--Prompt_C2BCE8F8E2C24403A71CA4B7F7521F5B_F659E9F3F8574A72BE92206596C423D5 ";

    // replacing standard prompt in order to determine end of command output
    process.StandardInput.WriteLine("prompt " + prompt);
    process.StandardInput.Flush();
    process.StandardOutput.ReadLine();
    process.StandardOutput.ReadLine();

    var result = new List<string>();

    try {
        var commandResult = new StringBuilder();

        foreach (var command in commands) {
            process.StandardInput.WriteLine(command);
            process.StandardInput.WriteLine();
            process.StandardInput.Flush();

            process.StandardOutput.ReadLine();

            while (true) {
                var line = process.StandardOutput.ReadLine();

                if (line == prompt) // end of command output
                    break;

                commandResult.AppendLine(line);
            }

            result.Add(commandResult.ToString());

            commandResult.Clear();

        }
    } finally {
        process.Kill();
    }

    return result;
}

It works well but it looks like one big hack.

I'd recommend you to use process per command instead.

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