HOWTO: Programmatically Force a Logoff on Windows 95

• Microsoft Win32 Application Programming Interface (API) included with: - Microsoft Windows 95

SUMMARY

You can use the Win32 API ExitWindowsEx() on Windows NT to force a logoff. You accomplish this by combining the EWX_LOGOFF and EWX_FORCE flags. Unfortunately, this combination is not supported on Windows 95.

You can duplicate this capability on Windows 95 by taking some additional steps before calling ExitWindowsEx().

MORE INFORMATION

ExitWindowsEx() with the EWX_LOGOFF flag alone does not force non- responsive applications to close. To achieve this, follow these steps:

1. Enumerate top-level windows with the EnumWindows() API.

2. In the EnumWindowsProc, ask each application to shut down by sending it the WM_QUERYENDSESSION message.

3. If the application responds positively, then send the WM_ENDSESSION message to direct the application to terminate.

4. If the application responds negatively, terminate the application with the TerminateProcess() API.

5. Once all applications with top-level windows have been shut down in this manner, you can call ExitWindowsEx(EWX_LOGOFF) with a reasonable assurance that the logoff operation will complete.

NOTE: This method is not 100% successful. There are a few applications that cause ExitWindowsEx() to fail. This article will be updated when more information is available.

NOTE: ExitWindowsEx does not work correctly if it is called from a Win32 Console application. This must be a Windows application to work properly.

Sample Code

The following sample code demonstrates the technique:

   #include <windows.h>

   BOOL CALLBACK EnumWindowsProc(
       HWND hwnd,
       DWORD lParam
       );

   //
   // EnumWindowsProc must be called from a windows
   // application on Windows 95
   //
   int WINAPI WinMain(
       HINSTANCE hInstance,
       HINSTANCE hPrevInstance,
       LPSTR lpCmdLine,
       int nCmdShow
       )
   {
       //
       // close all open applications
       //
       EnumWindows(EnumWindowsProc, 0);

       // Now do a regular logoff
       ExitWindowsEx(EWX_LOGOFF , 0);

   }

   BOOL CALLBACK EnumWindowsProc(
       HWND hwnd,
       DWORD lParam
       )
   {
       DWORD      pid = 0;
       LRESULT    lResult;
       HANDLE     hProcess;
       DWORD      dwResult;

       lResult = SendMessageTimeout(
           hwnd,
           WM_QUERYENDSESSION,
           0,
           ENDSESSION_LOGOFF,
           SMTO_ABORTIFHUNG,
           2000,
           &dwResult);

       if( lResult )
       {
          //
          // application will terminate nicely so let it
          //
          lResult = SendMessageTimeout(
              hwnd,
              WM_ENDSESSION,
              TRUE,
              ENDSESSION_LOGOFF,
              SMTO_ABORTIFHUNG,
              2000,
              &dwResult);

       }
       else  // we have to take more forceful measures
       {
           //
           // get the processid for this window
           //
           GetWindowThreadProcessId( hwnd, &pid );
           //
           // open the process with all access
           //
           hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
           //
           // bye-bye
           //
           TerminateProcess(hProcess, 0);

       }
       //
       // continue the enumeration
       //
       return TRUE;
   }