* VB-CODE (2)
Tip 92: Using the Shell Statement to Execute MS-DOS Programs

May 22, 1995

Abstract
From within a Visual Basic® application, you can execute an MS-DOS®
program. This article explains how to use the Shell statement in
conjunction with the Windows® application programming interface (API)
GetNumTasks function to execute an MS-DOS program.

Running MS-DOS Programs
A very popular set of utilities called PKZIP and PKUNZIP can be found
on bulletin board systems throughout the world. These two utilities
are used to compress and decompress a group of related files. The
resulting ZIP file can then be distributed as one single entity.
Because these programs are used by people daily, you may need to allow
your user to execute these MS-DOS programs (or an entirely different
MS-DOS program) from within your Visual Basic® application program.

Visual Basic's Shell function can be used to execute another program.
To run a program, you would issue the statement:

X = Shell("program name",[windowstate]])

The program name must be a valid MS-DOS or Windows®-based-application
name and may optionally include any command-line parameters needed by
the program. The second parameter tells Visual Basic how to execute
the program. There are five possible values for this argument, as
follows:

1 Normal size, program retains focus
2 Minimized, program retains focus
3 Maximized, program retains focus
4 Normal size, Visual Basic application retains focus
5 Minimized, program does not retain focus

While the MS-DOS program is executing, you can use the SendKeys
statement to send specific keystrokes to the application. In this
manner, you can actually control what the MS-DOS program does or
provide some required input.
In addition, you can determine when the secondary program has
terminated by using the GetNumTasks function. To use the GetNumTasks
function in your Visual Basic application, you must include the
following Declare statement in the Global Module or General
Declarations section of your form:

Private Declare Function GetNumTasks Lib "Kernel" () As Integer

The GetNumTasks function does not require any arguments but simply
returns an integer value set to the number of tasks that are currently
running under Windows. Therefore, to determine when your MS-DOS
program has finished executing, call GetNumTasks first, saving the
value it returns in a variable. After the MS-DOS program has finished
executing, call the GetNumTasks function a second time to find out if
the number of tasks has decreased by a value of one. If the value has
decreased, you know that your MS-DOS program has finished executing
and you can return control to your Visual Basic application.

Example Program
This program shows how you can use the Shell function and the
GetNumTasks function to execute an MS-DOS program. This program
assumes that you have the PKUNZIP program stored in the UTILS
directory and that you have previously created a destination
directory called DESTDIR on your hard drive.

 1. Create a new project in Visual Basic. Form1 is created by default.
 2. Add the following statements to the General Declarations section
    of Form1:

Dim ActiveApps As Integer
Private Declare Function GetNumTasks Lib "Kernel" () As Integer

 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 AppDir As String
    Dim Zip As String
    Dim Y As Integer
    Dim X As Integer

    AppDir = "c:\destdir"
    ActiveApps = GetNumTasks()

    Zip = "c:\utils\pkunzip " & "c:\destdir\" & "test.zip" & " " & AppDir
    X = Shell(Zip, 2)
    SendKeys "%{enter}EXIT%{ }n"

    Do While GetNumTasks() <> ActiveApps
        Y = DoEvents()
    Loop
    MsgBox "Pkunzip is finished", 0, "Demo Program"
End Sub

Additional References
Knowledge Base Q96844. "How to Determine When a Shelled Process Has
   Terminated."
"SendKeys Statement." (Product Documentation, Office Developer's
   Kit 1.0, Visual Basic 3.0 Professional Edition, Language Reference)
"Shell Function." (Product Documentation, Office Developer's
   Kit 1.0, Visual Basic 3.0 Professional Edition, Language Reference)