VB3 Using ExitWindowsExec() in VB to Run MS-DOS Batch File

The information in this article applies to:

- Standard and Professional Editions of Microsoft Visual Basic for

  Windows, versions 2.0 and 3.0

SUMMARY

The ExitWindowsExec() function terminates Windows, runs a specified MS-DOS application, and then restarts Windows. The information in this article shows you how to call this function from Microsoft Visual Basic.

MORE INFORMATION

The ExitWindowsExec() function is typically used by installation programs to replace components of Windows which are active when Windows is running. Normally, you'd want to run an MS-DOS batch file that performs the file copying while Windows is temporarily shut down. The declaration for ExitWindowsExec() is as follows:

   ' Place the following declaration on one, single line:
   Declare Function ExitWindowsExec Lib "User" (ByVal lpszExe As String,
      ByVal lpszParams As Any) As Integer

First Parameter: lpszExe$

The first parameter for ExitWindowsExec(), lpszExe$, should be a string containing the fully qualified path to the executable file you want to run. This string must contain no more than 127 characters. For batch files, you'll need to specify COMMAND.COM as the file -- C:\DOS\COMMAND.COM. To get the fully qualified path in Visual Basic to COMMAND.COM, you can use the Environ$ function:

   lpszExe$ = Environ$("COMSPEC")

Second Parameter: lpszParams$

The second parameter for ExitWindowsExec(), lpszParams$, should be a string containing any necessary parameters for the executable file. If no parameters are necessary, pass a long integer 0 such as 0&.

To execute a batch file, however, this is where you specify the path to the batch file and any parameters it needs. Also, you need to preface the string with the /c switch which tells MS-DOS to invoke a copy of COMMAND.COM. Here is an example:

   lpszParams$ = "/C C:\DIRNAME\GENERIC.BAT  PARAMETER1 PARAMETER2"

Step-by-Step Example

1. Using either NotePad in Windows or Edit in MS-DOS, create a batch file in the root directory of your hard disk called C:\RUNIT.BAT. Give it the following contents:

   @echo off echo Making Backup of autoexec.bat copy c:\autoexec.bat c:\*.bak echo Done

2. Start a new project in Visual Basic (Alt, F, N). Form1 is created by default.

3. Add the following declaration to the General Declarations section of the form:

      ' Place the following declaration on one, single line:
      Declare Function ExitWindowsExec Lib "User" (ByVal lpszExe As String,
         ByVal lpszParams As Any) As Integer
   
   

4. Add a command button (Command1) to the form, and place the following code in the Click() event.

      Sub Command1_Click ()
         sComspec$ = Environ$("COMSPEC")
         ret% = ExitWindowsExec(sComspec$,  "/c c:\runit.bat")
      End Sub
   
   

5. Save the project (Alt, F, V). Then press the F5 key to run the program. Click the command button to exit Windows, run the batch file, and then restart Windows.