Running Dos program in Visual Basic 
Author Message
 Running Dos program in Visual Basic

Dear All.

I have a couple of questions that I hope somebody can help me with.

I am running Visual Basic 4 and I would like to be able to run a Dos based
EXE program from within the Visual basic application.
The Dos based program is a program that runs routines based on command
switches entered on the command line.  

For example
                        COMM I0000 F1 T1 .......

The two questions I have are:

1: How do I run the DOS program within the VB application and stop further
processing of the VB application until the DOS application has finished.

2:  The DOS program returns an error message using the DOS interrupts, how
do I read these error messages back into my VB application.

Any help on these two questions would be very much appreciated.

Mon, 27 Dec 1999 03:00:00 GMT  
 Running Dos program in Visual Basic


        The solution to this problem depends on whether you are running in a 16bit
or 32bit
environment.  For the first question:

I found an article for calling a program In a 32 bit environment:
Tip 173: Launching Applications in Visual Basic

December 5, 1995


This article explains how to control the way in which a launched Microsoft?
Visual Basic? application is run.

Using the CreateProcess Function to Launch Applications

Under the Microsoft? Windows? 95 operating system, you can use the Windows
application programming interface (API) CreateProcess function to load and
run any application (or process) you want. Using this function, you have
complete control over how the launched application is run.

To use the CreateProcess function, add the following Declare statement to
the General Declarations section of your Microsoft Visual Basic? project or
to a BAS module:

Declare Function CreateProcessA Lib "kernel32" (ByVal lpApplicationName As
   ByVal lpCommandLine As String, ByVal lpProcessAttributes As Long, ByVal
   lpThreadAttributes As Long, ByVal bInheritHandles As Long, ByVal
   dwCreationFlags As Long, ByVal lpEnvironment As Long, ByVal
   lpCurrentDirectory As Long, lpStartupInfo As STARTUPINFO,
   lpProcessInformation As PROCESS_INFORMATION) As Long

As you can see, the CreateProcess function requires ten arguments, as


The name of the process you want to launch.


The command line to be passed to the launched process.


Points to a SECURITY_ATTRIBUTES structure for the created process.


Points to a SECURITY_ATTRIBUTES structure for the primary thread of the
created process.


If True, the created process inherits handles from the calling application.


A combination of one or more creation flags for controlling the priority
class and the creation of the process.


Points to an environment block for the new process. If set to NULL, the new
process uses the calling process's environment block.


A string containing the drive and directory for the new process. If NULL,
the calling process's drive and directory are used.


A STARTUPINFO structure that specifies the appearance of the main window
for the new process.


A PROCESS_INFORMATION structure that receives identification information
about the new process.

The example program below launches the Windows 95 Notepad application. Note
that you specify the complete path to Notepad and launch the application as
a normal process (NORMAL_PRIORITY_CLASS).

After you call the CreateProcess function to launch the Notepad
application, notice that Notepad retains the focus. You cannot switch to
another running application. This is accomplished by executing the Windows
API WaitForSingleObject function.

The WaitForSingleObject function forces the system to wait until a specific
process has finished its work. You pass the handle of the process you want
to wait for and the length of time, in milliseconds, to pause. In the
example program below, the time-out value is set to INFINITE, which means
that the system will not resume running until the user has quit Notepad.

The final step you must perform, after the user has quit Notepad, is to
close the open handle for the just-launched process. This removes all
references to Notepad having been launched.

Example Program

This program shows how to launch a Windows or MS-DOS? application from
within Microsoft Visual Basic. Control remains with the launched
application until you quit that application.

1.Create a new project in Visual Basic. Form1 is created by default.2.Add a
Command Button control to Form1. Command1 is created by default.3.Add the
following code to the Click event for Command1:

Private Sub Command1_Click()
    Dim AppToLaunch As String
    AppToLaunch = "c:\windows\notepad.exe"
    Call ExecuteAndWait(AppToLaunch)
End Sub

4.Create a new subroutine called ExecuteAndWait. Add the following code to
this subroutine:

Public Sub ExecuteAndWait(cmdline$)
    Dim NameStart As STARTUPINFO
    Dim X As Long

    NameStart.cb = Len(NameStart)
    X = CreateProcessA(0&, cmdline$, 0&, 0&, 1&, NORMAL_PRIORITY_CLASS,
       0&, 0&, NameStart, NameOfProc)
    X = WaitForSingleObject(NameOfProc.hProcess, INFINITE)
    X = CloseHandle(NameOfProc.hProcess)
End Sub

5.From the Visual Basic Insert menu, select Module to add a new module to
your project. Module1.Bas is created by default.6.Add the following code to
Module1.Bas (note that each Declare statement must be typed as a single
line of code):

    cb As Long
    lpReserved As String
    lpDesktop As String
    lpTitle As String
    dwX As Long
    dwY As Long
    dwXSize As Long
    dwYSize As Long
    dwXCountChars As Long
    dwYCountChars As Long
    dwFillAttribute As Long
    dwFlags As Long
    wShowWindow As Integer
    cbReserved2 As Integer
    lpReserved2 As Long
    hStdInput As Long
    hStdOutput As Long
    hStdError As Long
End Type
    hProcess As Long
    hThread As Long
    dwProcessID As Long
    dwThreadID As Long
End Type
Global Const INFINITE = -1&
Declare Function CloseHandle Lib "kernel32" (hObject As Long) As Boolean
Declare Function WaitForSingleObject Lib "kernel32" (ByVal hHandle As Long,

   ByVal dwMilliseconds As Long) As Long
Declare Function CreateProcessA Lib "kernel32" (ByVal lpApplicationName As
   ByVal lpCommandLine As String, ByVal lpProcessAttributes As Long, ByVal
   lpThreadAttributes As Long, ByVal bInheritHandles As Long, ByVal
   dwCreationFlags As Long, ByVal lpEnvironment As Long, ByVal
   lpCurrentDirectory As Long, lpStartupInfo As STARTUPINFO,
   lpProcessInformation As PROCESS_INFORMATION) As Long

Run the example program by pressing f5. Click the Command Button control.
This immediately starts the Windows Notepad application. Notice that you
are unable to switch to another running application until you quit Notepad.

In a 16bit environment the following should work:
Step-by-Step Example

1.Start Visual Basic for Windows or from the File menu, choose New Project
(ALT, F, N) if Visual Basic for Windows is already running. Form1 is
created by default. 2.Add the following code to the general declarations
section of Form1:

Declare Function GetModuleUsage% Lib "Kernel" (ByVal hModule%) 3.Add the
following code to the Form_Click event procedure of Form1:

Sub Form_Click ()

      x% = Shell("NOTEPAD.EXE")       ' Modify the path as necessary.
      While GetModuleUsage(x%) > 0    ' Has Shelled program finished?
         z% = DoEvents()              ' If not, yield to Windows.
      MsgBox "Shelled application just terminated", 64

End Sub 4.From the Run menu, choose Start (ALT, R, S) to run the program.
5.Using the mouse, click in the Form1 window. At this point, the Notepad
application is shelled.

The MsgBox statement following the Shell() Function is not executed because
the While loop prevents it. The message box does not appear until Notepad
is closed when the user chooses Exit from Notepad's File menu (ALT, F, X).

By the way...these article snippets are taken from Microsoft's Knowledge
Base which is available
on-line from their website....

In response to your second question, the only way I've found is to redirect
the ouput of the
DOS program to a text file that can be read by your application after the
program has finished.
I know standard output is redirected like DIR *.* > DIRLIST.TXT but if that
is not sufficient than
you may need to find another way.

I hope some of this helps ya!


Tue, 28 Dec 1999 03:00:00 GMT  
 [ 2 post ] 

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