How To Attach a Console Window to Your Visual Basic Program

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Article ID: 171654 - View products that this article applies to.
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SUMMARY

This article demonstrates attaching a console window to your Visual Basic application, writing to it, and running another application in the console window.

MORE INFORMATION

If a Visual Basic application is started from a console application, the operating system automatically detaches it from the console, preventing the Visual Basic application from interacting with it. This article does not provide a method to prevent this from happening, but does demonstrate creating a new console window that your application can interact with. It also demonstrates running a console application (batch file, in this case) from Visual Basic, which utilizes the created console.

WARNING: ANY USE BY YOU OF THE CODE PROVIDED IN THIS ARTICLE IS AT YOUR OWN RISK. Microsoft provides this code "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.

Step-by-Step Example

  1. Use Notepad to create the following batch file:

    DIR /W

    and save it as C:\TEST.BAT
  2. In Visual Basic, create a new project with a form and a module.
  3. Type the following API declarations in the module:
       Option Explicit
    
       Declare Function AllocConsole Lib "kernel32" () As Long
       Declare Function FreeConsole Lib "kernel32" () As Long
       Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) _
               As Long
       Declare Function GetStdHandle Lib "kernel32" (ByVal _
               nStdHandle As Long) As Long
       Declare Function WriteConsole Lib "kernel32" Alias "WriteConsoleA" _
               (ByVal hConsoleOutput As Long, lpBuffer As Any, ByVal _
               nNumberOfCharsToWrite As Long, lpNumberOfCharsWritten As Long, _
               lpReserved As Any) As Long
    
       Public Const STD_OUTPUT_HANDLE = -11&
    
    						
  4. Add a CommandButton to the form and enter the following code:
       Dim hConsole As Long
    
       Private Sub Command1_Click()
       Dim Result As Long, sOut As String, cWritten As Long
         sOut = "Hi There" & vbCrLf
         Result = WriteConsole(hConsole, ByVal sOut, Len(sOut), cWritten, _
                               ByVal 0&)
         Shell "C:\TEST.BAT"
       End Sub
    
       Private Sub Form_Load()
         If AllocConsole() Then
           hConsole = GetStdHandle(STD_OUTPUT_HANDLE)
           If hConsole = 0 Then MsgBox "Couldn't allocate STDOUT"
         Else
           MsgBox "Couldn't allocate console"
         End If
       End Sub
    
       Private Sub Form_Unload(Cancel As Integer)
         CloseHandle hConsole
         FreeConsole
       End Sub
    
    						
  5. Run the application. A blank console window will appear.
  6. Click the CommandButton. Both the text in sOut and the output from the batch file will appear in the console.
  7. Close the form. The console window will terminate.
NOTES:
  1. If you run another application in the console, it will run asynchronously with your Visual Basic application. Output from the two applications can become interspersed.
  2. If the console application hasn't terminated prior to your Visual Basic application closing, the console window will remain open.
  3. If you close the console window, the Visual Basic EXE will terminate. If you are in the Visual Basic development environment (IDE), closing the console window will terminate the IDE and it may hang the console window. Use the Task Manager to terminate the task.

REFERENCES

Microsoft Windows SDK.

Properties

Article ID: 171654 - Last Review: June 29, 2004 - Revision: 4.1
APPLIES TO
  • Microsoft Visual Basic 6.0 Learning Edition
  • Microsoft Visual Basic 6.0 Professional Edition
  • Microsoft Visual Basic 6.0 Enterprise Edition
  • Microsoft Visual Basic 5.0 Control Creation Edition
  • Microsoft Visual Basic 5.0 Learning Edition
  • Microsoft Visual Basic 5.0 Professional Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition
  • Microsoft Visual Basic 4.0 Standard Edition
  • Microsoft Visual Basic 4.0 Professional Edition
  • Microsoft Visual Basic 4.0 32-Bit Enterprise Edition
Keywords: 
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