c# execute command line like command prompt?

Question

I want to write a c# code to execute some command prompt lines and store the result into a global variable in c# to be used for further processing in other part of the code in c#.

I bought a device and I installed its driver. The only way for me to obtain its data is using command line in command prompt. There is no API available. But, I want to do in c# so that is why I am having trouble.

I have some code and it doesn't works for some reason. Note, I used argument input = "date" is only for illustration purpose. My work is not using "date" but some arguments to obtain data.

static void Main(string[] args)
{
    System.Diagnostics.Process process = new System.Diagnostics.Process();
    System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo();
    startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
    // the cmd program
    startInfo.FileName = "cmd.exe";
    // set my arguments. date is just a dummy example. the real work isn't use date.
    startInfo.Arguments = "date";
    startInfo.RedirectStandardOutput = true;
    startInfo.UseShellExecute = false;
    process.StartInfo = startInfo;
    process.Start();
    // capture what is generated in command prompt
    var output = process.StandardOutput.ReadToEnd();
    // write output to console
    Console.WriteLine(output);
    process.WaitForExit();

    Console.Read();
}

Any help is appreciated.

Answer 1

you'll need to use /c date to get cmd to launch date like that.

static void Main(string[] args)
{
    System.Diagnostics.Process process = new System.Diagnostics.Process();
    System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo();
    startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
    // the cmd program
    startInfo.FileName = "cmd.exe";
    // set my arguments. date is just a dummy example. the real work isn't use date.
    startInfo.Arguments = "/c date";
    startInfo.RedirectStandardOutput = true;
    startInfo.UseShellExecute = false;
    process.StartInfo = startInfo;
    process.Start();
    // capture what is generated in command prompt
    var output = process.StandardOutput.ReadToEnd();
    // write output to console
    Console.WriteLine(output);
    process.WaitForExit();

    Console.Read();
}

the flags /c and /k are your friends when using cmd.exe to launch other programs. /c is used to execute a program then exit CMD. /k is used to execute a program then leave CMD running.

Answer 2

I would also guess not all applications use stderr and stdout properly so it is possible what you see in a "Console Application" is not delivering the information where you expect it.

If nothing more redirecting stderr as well, will also allow you to see if it is syntax related and the application is tossing an exception.

startInfo.RedirectStandardError = true;

I want to add to that, by wrapping it up in a class, you can interact with the cmd shell, not just run and return... If you are trying to automate an application silently, this is likely the approach you want...

I just wrote a sample of this for a guy in VB, the syntax is probably rough because I had not launched VB in years, but you get the gist of it and should be able to replicate in C# fairly easily. This was a rough draft How to type approach, not a piece of code I would call production ready, teach a man to fish sample ;)

#Region " Imports "

Imports System.Threading
Imports System.ComponentModel

#End Region

Namespace Common

    Public Class CmdShell

#Region " Variables "

        Private WithEvents ShellProcess As Process

#End Region

#Region " Events "

        ''' <summary>
        ''' Event indicating an asyc read of the command process's StdOut pipe has occured.
        ''' </summary>
        Public Event DataReceived As EventHandler(Of CmdShellDataReceivedEventArgs)

#End Region

#Region " Public Methods "

        Public Sub New()
            ThreadPool.QueueUserWorkItem(AddressOf ShellLoop, Nothing)
            Do Until Not ShellProcess Is Nothing : Loop
        End Sub

        ''' <param name="Value">String value to write to the StdIn pipe of the command process, (CRLF not required).</param>
        Public Sub Write(ByVal value As String)
            ShellProcess.StandardInput.WriteLine(value)
        End Sub

#End Region

#Region " Private Methods "

        Private Sub ShellLoop(ByVal state As Object)
            Try
                Dim SI As New ProcessStartInfo("cmd.exe")
                With SI
                    .Arguments = "/k"
                    .RedirectStandardInput = True
                    .RedirectStandardOutput = True
                    .RedirectStandardError = True
                    .UseShellExecute = False
                    .CreateNoWindow = True
                    .WorkingDirectory = Environ("windir")
                End With
                Try
                    ShellProcess = Process.Start(SI)
                    With ShellProcess
                        .BeginOutputReadLine()
                        .BeginErrorReadLine()
                        .WaitForExit()
                    End With
                Catch ex As Exception
                    With ex
                        Trace.WriteLine(.Message)
                        Trace.WriteLine(.Source)
                        Trace.WriteLine(.StackTrace)
                    End With
                End Try
            Catch ex As Exception
                With ex
                    Trace.WriteLine(.Message)
                    Trace.WriteLine(.Source)
                    Trace.WriteLine(.StackTrace)
                End With
            End Try
        End Sub

        Private Sub ShellProcess_ErrorDataReceived(ByVal sender As Object, ByVal e As System.Diagnostics.DataReceivedEventArgs) Handles ShellProcess.ErrorDataReceived
            If Not e.Data Is Nothing Then RaiseEvent DataReceived(Me, New CmdShellDataReceivedEventArgs(e.Data))
        End Sub

        Private Sub ShellProcess_OutputDataReceived(ByVal sender As Object, ByVal e As System.Diagnostics.DataReceivedEventArgs) Handles ShellProcess.OutputDataReceived
            If Not e.Data Is Nothing Then RaiseEvent DataReceived(Me, New CmdShellDataReceivedEventArgs(e.Data & Environment.NewLine))
        End Sub

#End Region

    End Class

    <EditorBrowsable(EditorBrowsableState.Never)> _
       Public Class CmdShellDataReceivedEventArgs : Inherits EventArgs
        Private _Value As String

        Public Sub New(ByVal value As String)
            _Value = value
        End Sub

        Public ReadOnly Property Value() As String
            Get
                Return _Value
            End Get
        End Property

    End Class

End Namespace

Just to make sure there were no pitfalls, I went ahead and did this dirty in c#

 public class cmdShell
    {
        private Process shellProcess;

        public delegate void onDataHandler(cmdShell sender, string e);
        public event onDataHandler onData;

        public cmdShell()
        {
            try
            {
                shellProcess = new Process();
                ProcessStartInfo si = new ProcessStartInfo("cmd.exe");
                si.Arguments = "/k";
                si.RedirectStandardInput = true;
                si.RedirectStandardOutput = true;
                si.RedirectStandardError = true;
                si.UseShellExecute = false;
                si.CreateNoWindow = true;
                si.WorkingDirectory = Environment.GetEnvironmentVariable("windir");
                shellProcess.StartInfo = si;
                shellProcess.OutputDataReceived += shellProcess_OutputDataReceived;
                shellProcess.ErrorDataReceived += shellProcess_ErrorDataReceived;
                shellProcess.Start();
                shellProcess.BeginErrorReadLine();
                shellProcess.BeginOutputReadLine();
            }
            catch (Exception ex)
            {
                Trace.WriteLine(ex.Message);
            }
        }

        void shellProcess_ErrorDataReceived(object sender, DataReceivedEventArgs e)
        {
            doOnData(e.Data);
        }

        void shellProcess_OutputDataReceived(object sender, DataReceivedEventArgs e)
        {
            doOnData(e.Data);
        }

        private void doOnData(string data)
        {
            if (onData != null) onData(this, data);
        }

        public void write(string data)
        {
            try
            {
                shellProcess.StandardInput.WriteLine(data);
            }
            catch (Exception ex)
            {
                Trace.WriteLine(ex.Message);
            }
        }
    }

So now using like this

cmdShell test = new cmdShell();
test.onData += test_onData;
test.write("ping 127.0.0.1");

with this on place

 void test_onData(cmdShell sender, string e)
        {
            Trace.WriteLine(e);
        }

You have a fully interactive cmd process to write to and receive async data from.

outputs to the window

C:\Windows>ping 127.0.0.1

Pinging 127.0.0.1 with 32 bytes of data:
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128

Ping statistics for 127.0.0.1:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 0ms, Average = 0ms

Coffee, sleep... lol

If you really want date...

cmdShell test = new cmdShell();
test.onData += test_onData;
test.write("date");

Yields output

C:\Windows>date
The current date is: Wed 10/08/2014

or

    cmdShell test = new cmdShell();
    test.onData += test_onData;
    test.write("echo %date%");

Yields output

C:\Windows>echo %date%
Wed 10/08/2014

By the way, in case you have not actually used the code yet, this method gives the data async, meaning as the program outputs it is delivered to you, so if you run a process that takes time, like 100 pings, traceroute, etc... you see them as they happen, not have to wait for it to complete and return.

Also you can pass commands back to the application during that, like canceling, reacting to and changing syntax, or simply running something else similar based on the result of the first run.

essentially you can treat it just like you were typing in a cmd window, and receiving the feedback there, wrap the whole think in a properly threaded form (Careful when updating windows controls from other threads), and you would have an emulated cmd prompt.