Continuous Shell Session

Question

Hello, I have been back and forth on a personal project to get an application using shell in VB.net for some experience. I have everything working great but I have come to a crossroads with a limitation. I have a process in my program that operates commands with shell, the problem is that for every command I send through runs its own shell session rather than a continuous single session. I very much enjoy figuring these things out but I am finding this subject matter rather hard to find in the communities.  Within this process, is it possible to keep the same session open rather than opening a new one for each input. example, if i run ping -t localhost and type it again, it will just create two instances of the the ping and send them both back to my textbox and so on. The other hindrance in this is that if i send a looping command such as ping -t in, i have no way to kill other than to close the program itself. Any input would be appreciated.

Public Class 

    Private cmd As String
    Delegate Sub AppendText(ByVal Textbox As TextBox, ByVal Text As String)
    Sub AppendToTextBox(ByVal Textbox As TextBox, ByVal Text As String)
        If Textbox.InvokeRequired Then
            Textbox.Invoke(New AppendText(AddressOf AppendToTextBox), Textbox, Text)
        Else
            Try
                Textbox.AppendText(Text & vbCrLf)
                Textbox.Update()
            Catch
            End Try
        End If
    End Sub

    Public Sub recieveScript(ByVal script As String)
        cmdProcess(script, addEntry:=False)
    End Sub
Public Sub cmdProcess(ByVal cmdInput As String, Optional ByVal addEntry As Boolean = True)

        Dim myProcess As Process = New Process
        Dim s As String = ""

        AddHandler myProcess.OutputDataReceived, AddressOf cmdOutput

        myProcess.StartInfo.FileName = "c:\windows\system32\cmd.exe"
        myProcess.StartInfo.UseShellExecute = False
        myProcess.StartInfo.CreateNoWindow = True
        myProcess.StartInfo.RedirectStandardInput = True
        myProcess.StartInfo.RedirectStandardOutput = True
        myProcess.StartInfo.RedirectStandardError = True
        myProcess.Start()
        myProcess.BeginOutputReadLine()
        Dim sIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sErr As System.IO.StreamReader = myProcess.StandardError
        sIn.AutoFlush = True
        sIn.Write(cmdInput & System.Environment.NewLine)
        sIn.Write("exit" & System.Environment.NewLine)
        cmdOutputTextBox.Text = s
        cmdOutputTextBox.Visible = True
        sIn.Close()
        sErr.Close()
        myProcess.Close()
    End Sub
    Public Sub cmdOutput(ByVal sendingProcess As Object, ByVal outLine As DataReceivedEventArgs)

        cmd = outLine.Data
        AppendToTextBox(cmdOutputTextBox, outLine.Data)

    End Sub
Private Function Button1_Click_2(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bntSend.Click

        Dim cmdInput As String
        cmdInput = txtCMD.Text
        cmdProcess(cmdInput)
        Return cmdInput

        txtCMD.Text = ""

    End Function
End Class

Thank you,

Answer 1

The problem is that for every command you send, you start up the cmd.exe process, execute the command, and then close it.  Instead, create or start the cmd process when the app starts and keep a referecne to it open and then only close it when you  close your application.

Keep references to the input and output streams and in your cmdProcess method just write the commands to the streams.

Answer 2

Hey thank you so much for the advice, this works great. I did run into a new bug though and maybe you can identify it if I incorporated your advice wrong. Say for example I send a simply command such as "dir" into the shell, it returns everything wonderfully, however say I typed it again. Now in the output I will get each line twice, then three then four. Its like process is stacking up.

Here was the adjustment I made based on what I understood from your advice.

Public Class program

    Private cmd As String
    Delegate Sub AppendText(ByVal Textbox As TextBox, ByVal Text As String)

    Dim myProcess As Process = New Process
    Dim s As String = ""

    Dim cmdID As Integer = 0

    Dim sIn As System.IO.StreamWriter
    Dim sErr As System.IO.StreamReader

    Sub AppendToTextBox(ByVal Textbox As TextBox, ByVal Text As String)
        If Textbox.InvokeRequired Then
            Textbox.Invoke(New AppendText(AddressOf AppendToTextBox), Textbox, Text)
        Else
            Try
                Textbox.AppendText(Text & vbCrLf)
                Textbox.Update()
            Catch
            End Try
        End If
    End Sub

    Public Sub recieveScript(ByVal script As String)
        cmdProcess(script, addEntry:=False)
    End Sub

    Public Sub cmdProcess(ByVal cmdInput As String, Optional ByVal addEntry As Boolean = True)


        AddHandler myProcess.OutputDataReceived, AddressOf cmdOutput

        sIn.AutoFlush = True
        sIn.Write(cmdInput & System.Environment.NewLine)

        cmdOutputTextBox.Text = s
        cmdOutputTextBox.Visible = True

    End Sub

    Public Sub cmdOutput(ByVal sendingProcess As Object, ByVal outLine As DataReceivedEventArgs)

        cmd = outLine.Data
        AppendToTextBox(cmdOutputTextBox, outLine.Data)

    End Sub
    
    Private Sub program_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        myProcess.StartInfo.FileName = "c:\windows\system32\cmd.exe"
        myProcess.StartInfo.UseShellExecute = False
        myProcess.StartInfo.CreateNoWindow = True
        myProcess.StartInfo.RedirectStandardInput = True
        myProcess.StartInfo.RedirectStandardOutput = True
        myProcess.StartInfo.RedirectStandardError = True
        myProcess.Start()
        myProcess.BeginOutputReadLine()
        sIn = myProcess.StandardInput
        sErr = myProcess.StandardError
        cmdID = myProcess.Id

    End Sub

Private Function Button1_Click_2(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bntSend.Click

        Dim cmdInput As String
        cmdInput = txtCMD.Text
        cmdProcess(cmdInput)
        Return cmdInput

        txtCMD.Text = ""

    End Function

End class

Answer 3

try these

Public Class Form1
    Private cmd As String
    Public OPTB As TextBox
    Delegate Sub AppendText(ByVal Textbox As TextBox, ByVal Text As String)
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim ScriptLines As New List(Of String)
        ScriptLines.Add("cd blabal")
        ScriptLines.Add("dir /w /ad")
        'etc...
        ExecuteCmds(ScriptLines, TextBox1)
    End Sub
    Sub AppendToTextBox(ByVal Textbox As TextBox, ByVal Text As String)
        If Textbox.InvokeRequired Then
            Textbox.Invoke(New AppendText(AddressOf AppendToTextBox), Textbox, Text)
        Else
            Try
                Textbox.AppendText(Text & vbCrLf)
                Textbox.Update()
            Catch
            End Try
        End If
    End Sub
    Public Sub ExecuteCmds(ByVal cmdInput As List(Of String), Optional ByVal OutPutTextBox As TextBox = Nothing, Optional ByVal addEntry As Boolean = True)
        Try
            OPTB = OutPutTextBox
            Dim myProcess As Process = New Process
            Dim s As String = ""
            AddHandler myProcess.OutputDataReceived, AddressOf cmdOutput
            myProcess.StartInfo.FileName = "c:\windows\system32\cmd.exe"
            myProcess.StartInfo.Verb = "runas"
            myProcess.StartInfo.UseShellExecute = False
            myProcess.StartInfo.CreateNoWindow = True
            myProcess.StartInfo.RedirectStandardInput = True
            myProcess.StartInfo.RedirectStandardOutput = True
            myProcess.StartInfo.RedirectStandardError = True
            myProcess.Start()
            myProcess.BeginOutputReadLine()
            Dim sIn As System.IO.StreamWriter = myProcess.StandardInput
            Dim sErr As System.IO.StreamReader = myProcess.StandardError
            sIn.AutoFlush = True
            For Each ss As String In cmdInput
                sIn.Write(ss & System.Environment.NewLine)
            Next
            If Not OutPutTextBox Is Nothing Then
                OutPutTextBox.Text = s
                OutPutTextBox.Visible = True
            End If
            sIn.Close()
            sErr.Close()
            myProcess.Close()
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try

    End Sub
    Public Sub cmdOutput(ByVal sendingProcess As Object, ByVal outLine As DataReceivedEventArgs)
        cmd = outLine.Data
        If Not OPTB Is Nothing Then
            AppendToTextBox(OPTB, outLine.Data)
        End If
    End Sub
End Class

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