Tip 191: Shelling to Other Applications

December 5, 1995

Abstract
This article explains how to run MS-DOS?-based and Microsoft
Windows?-based applications from within a Microsoft Visual Basic?
application.

Running MS-DOS and Windows Applications
When you want to run an MS-DOS?-based or Microsoft? Windows?-based
application, you can use the Windows application programming interface
(API) OpenProcess function. The OpenProcess function allows you to
control how the application is run.

In the example program below, you use the OpenProcess function to launch
the Notepad application. The OpenProcess function returns the handle of
the newly opened process (that is, application). When you have the process
handle for Notepad, you can use the Windows API GetExitCodeProcess
function to determine whether Notepad is still running in memory.

The GetExitCodeProcess function returns a value of STILL_ACTIVE if the
opened process is still running in memory. Knowing this, you can
periodically check the status of the Notepad application in a Do-While
loop. When the example program finds that Notepad is not running, the
example program displays a message that Notepad was indeed terminated.

Example Program
This program shows how to run an MS-DOS-based or Windows-based application
in the background. The application continues running in the background
until the user terminates it.

 1. Create a new project in Visual Basic. Form1 is created by default.
 2. Add the following Constant and Declare statements to the General
    Declarations section of Form1 (note that each Declare statement
    must be typed as a single line of code):

Private Declare Function OpenProcess Lib "kernel32"
   (ByVal dwDesiredAccess As Long, ByVal bInheritHandle
   As Long, ByVal dwProcessId As Long) As Long
Private Declare Function GetExitCodeProcess Lib "kernel32"
   (ByVal hProcess As Long, lpExitCode As Long) As Long
Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds
   As Long)
Const STILL_ACTIVE = &H103
Const PROCESS_QUERY_INFORMATION = &H400

 3. Add a Command Button control to Form1. Command1 is created by default.
 4. Add the following code to the Click event for Command1:

Private Sub Command1_Click()
    Dim JobToDo As String
    JobToDo = "c:\windows\notepad.exe"
    Shell32Bit JobToDo
End Sub

 5. Create a new subroutine called Shell32Bit. Add the following code to
    this subroutine:

Sub Shell32Bit(ByVal JobToDo As String)
    Dim hProcess As Long
    Dim RetVal As Long
    'The next line launches JobToDo as icon,
    'captures process ID
    hProcess = OpenProcess(PROCESS_QUERY_INFORMATION, Flase, Shell(JobToDo, 6))
    Do
        'Get the status of the process
        GetExitCodeProcess hProcess, RetVal
        'Sleep command recommended as well
        'as DoEvents
        DoEvents: Sleep 100
    'Loop while the process is active
    Loop While RetVal = STILL_ACTIVE
    MsgBox "Notepad terminated by user"
End Sub

Run the example program by pressing F5. Click the Command Button control.
The example program runs the Windows Notepad application. Notice that the
Notepad icon appears in the Windows taskbar.

Notepad runs in the background until you quit it. The example program
displays a message box that indicates that Notepad was terminated.