Microsoft KB Archive/168796

= DOC: ExitWindows Function Declaration Incorrect in API Viewer =

Article ID: 168796

Article Last Modified on 6/24/2004

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APPLIES TO


 * Microsoft Visual Basic 5.0 Control Creation Edition
 * Microsoft Visual Basic 5.0 Learning Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 6.0 Professional Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition
 * Microsoft Visual Basic 6.0 Enterprise Edition
 * Microsoft Visual Basic 4.0 Standard Edition
 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 32-Bit Enterprise Edition
 * Microsoft Visual Basic for Applications 5.0
 * Microsoft Visual Basic for Applications 6.0

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This article was previously published under Q168796



SUMMARY
This article demonstrates how to programmatically restart or log off a computer in Visual Basic. The sample code shown in this article creates a project that can normally or forcibly perform these functions on a computer with a Windows 95, Windows 98, Windows Me, Windows 2000, or Windows NT operating system. A normal procedure allows the user the opportunity to close all open programs before executing a restart or log off. A forced procedure automatically closes all open programs before executing a restart or log off.



MORE INFORMATION
The Windows API has a function to programmatically shut down and restart or log off a computer. The Boolean function ExitWindowsEx performs the following tasks:


 * Shut down the system.
 * Shut down and restart the system.
 * Log off and force all running applications to terminate.

The function returns a value as soon as the function initiates a shutdown. The function returns True if the shutdown will be successful and False if the function fails. Extended error information is available by calling the function GetLastError.

To use this function under Windows NT and Windows 2000, enable the SE_SHUTDOWN_NAME security privilege by using the AdjustTokenPrivileges function. Windows 95, Windows 98, and Windows Me do not support or require these security privileges.

The flag passed to the ExitWindowsEx function determines whether the function performs a forced or normal log off, shutdown, or a restart. You can pass the following flags to this function:


 * EWX_FORCE - Forcibly terminates processes that do not respond to a shut down command.

NOTE: Using this flag can cause data loss because Windows does not send the messages WM_QUERYENDSESSION and WM_ENDSESSION to applications currently running in the computer. Use this flag only in cases where data loss is not critical.
 * EWX_LOGOFF - terminates all processes and then logs off the computer.
 * EWX_POWEROFF - shuts down the computer and turns off the power in systems with a power-off feature. Under Windows NT and Windows 2000, the process that calls the ExitWindowsEx function with this flag must have the SE_SHUTDOWN_NAME privilege. Windows 95, Windows 98, and Windows Me do not support or require this privilege.
 * EWX_REBOOT [ASCII 150] shuts down and then restarts the computer. Under Windows NT and Windows 2000, the process that calls the ExitWindowsEx function with this flag must have the SE_SHUTDOWN_NAME privilege. Windows 95, Windows 98, and Windows Me do not support or require this privilege.
 * EWX_SHUTDOWN - shuts down the computer to a point that is safe to turn off the power. All file buffers have been flushed to disk, and all running processes have stopped. Under Windows NT and Windows 2000, the process that calls the ExitWindowsEx function with this flag must have the SE_SHUTDOWN_NAME privilege. Windows 95, Windows 98, and Windows Me do not support or require this privilege.

Sample Program
The sample program illustrates how you can use the ExitWindowsEx function to perform a shut down or log off. The project has a form with four command buttons. The program begins by determining the operating system through the GetVersion function. The operating system determines whether privileges should be set in order to perform a log off or shut down. The operating system version is stored in a variable and is then displayed in a message box. Close the message box and a form appears with four command buttons. The command buttons perform the following tasks:
 * 1) Log Off - calls the ExitWindowsEx function with the EWX_Logoff flag to log off the user. The user can shut down all running programs.
 * 2) Forced Log off - calls the ExitWindowsEx function with the EWX_Logoff or the EWX_Forced flags to initiate a forced log off.
 * 3) Shut Down - if the operating system is Windows NT or Windows 2000, the correct privilege is set. A message box then displays the last error value of the process thread. Otherwise, the ExitWindowsEx function is called with the EWX_Shutdown flag.
 * 4) Forced Shut Down - if the operating system is Windows NT or Windows 2000, the correct privilege is set. A message box then displays the last error value of the process thread. Otherwise, the ExitWindowsEx function is called with the EWX_Shutdown or the EWX_Force flags to initiate a forced shutdown.

Steps To Reproduce Behavior
 Start the development environment and add a new form (Access and Visual Basic) or UserForm (other Office 97 programs). In Excel 95, you can call the code from the Tools|Macro menu.  Place the following objects on the form (or UserForm) and set the appropriate properties:   Control          Name               Caption ---  Command Button   cmdLogoff          Log Off Command Button  cmdForceLogoff     Force Log Off Command Button  cmdShutdown        Shut Down Command Button  cmdForceShutdown   Forced Shut Down   Copy and paste the following code to the form's Module: Option Explicit Private Const EWX_LogOff As Long = 0 Private Const EWX_SHUTDOWN As Long = 1 Private Const EWX_REBOOT As Long = 2 Private Const EWX_FORCE As Long = 4 Private Const EWX_POWEROFF As Long = 8

'The ExitWindowsEx function either logs off, shuts down, or shuts 'down and restarts the system. Private Declare Function ExitWindowsEx Lib "user32" _ (ByVal dwOptions As Long, _         ByVal dwReserved As Long) As Long

'The GetLastError function returns the calling thread's last-error 'code value. The last-error code is maintained on a per-thread basis. 'Multiple threads do not overwrite each other's last-error code. Private Declare Function GetLastError Lib "kernel32" As Long

Private Const mlngWindows95 = 0 Private Const mlngWindowsNT = 1

Public glngWhichWindows32 As Long

'The GetVersion function returns the operating system in use. Private Declare Function GetVersion Lib "kernel32" As Long

Private Type LUID UsedPart As Long IgnoredForNowHigh32BitPart As Long End Type

Private Type LUID_AND_ATTRIBUTES TheLuid As LUID Attributes As Long End Type

Private Type TOKEN_PRIVILEGES PrivilegeCount As Long TheLuid As LUID Attributes As Long End Type

'The GetCurrentProcess function returns a pseudohandle for the 'current process. Private Declare Function GetCurrentProcess Lib "kernel32" As Long

'The OpenProcessToken function opens the access token associated with 'a process. Private Declare Function OpenProcessToken Lib "advapi32" _ (ByVal ProcessHandle As Long, _         ByVal DesiredAccess As Long, _          TokenHandle As Long) As Long

'The LookupPrivilegeValue function retrieves the locally unique 'identifier (LUID) used on a specified system to locally represent 'the specified privilege name. Private Declare Function LookupPrivilegeValue Lib "advapi32" _ Alias "LookupPrivilegeValueA" _ (ByVal lpSystemName As String, _         ByVal lpName As String, _          lpLuid As LUID) As Long

'The AdjustTokenPrivileges function enables or disables privileges 'in the specified access token. Enabling or disabling privileges 'in an access token requires TOKEN_ADJUST_PRIVILEGES access. Private Declare Function AdjustTokenPrivileges Lib "advapi32" _ (ByVal TokenHandle As Long, _         ByVal DisableAllPrivileges As Long, _          NewState As TOKEN_PRIVILEGES, _          ByVal BufferLength As Long, _          PreviousState As TOKEN_PRIVILEGES, _          ReturnLength As Long) As Long

Private Declare Sub SetLastError Lib "kernel32" _ (ByVal dwErrCode As Long)

Private Sub AdjustToken

'********************************************************************     '* This procedure sets the proper privileges to allow a log off or a      '* shut down to occur under Windows NT. '********************************************************************

Const TOKEN_ADJUST_PRIVILEGES = &H20 Const TOKEN_QUERY = &H8 Const SE_PRIVILEGE_ENABLED = &H2

Dim hdlProcessHandle As Long Dim hdlTokenHandle As Long Dim tmpLuid As LUID Dim tkp As TOKEN_PRIVILEGES Dim tkpNewButIgnored As TOKEN_PRIVILEGES Dim lBufferNeeded As Long

'Set the error code of the last thread to zero using the 'SetLast Error function. Do this so that the GetLastError 'function does not return a value other than zero for no        'apparent reason. SetLastError 0

'Use the GetCurrentProcess function to set the hdlProcessHandle 'variable. hdlProcessHandle = GetCurrentProcess

If GetLastError <> 0 Then MsgBox "GetCurrentProcess error==" & GetLastError End If

OpenProcessToken hdlProcessHandle, _ (TOKEN_ADJUST_PRIVILEGES Or TOKEN_QUERY), hdlTokenHandle

If GetLastError <> 0 Then MsgBox "OpenProcessToken error==" & GetLastError End If

'Get the LUID for shutdown privilege LookupPrivilegeValue "", "SeShutdownPrivilege", tmpLuid

If GetLastError <> 0 Then MsgBox "LookupPrivilegeValue error==" & GetLastError End If

tkp.PrivilegeCount = 1   ' One privilege to set tkp.TheLuid = tmpLuid tkp.Attributes = SE_PRIVILEGE_ENABLED

'Enable the shutdown privilege in the access token of this process AdjustTokenPrivileges hdlTokenHandle, _ False, _ tkp, _ Len(tkpNewButIgnored), _ tkpNewButIgnored, _ lBufferNeeded

If GetLastError <> 0 Then MsgBox "AdjustTokenPrivileges error==" & GetLastError End If

End Sub

Private Sub cmdLogoff_Click

ExitWindowsEx (EWX_LogOff), &HFFFF MsgBox "ExitWindowsEx's GetLastError " & GetLastError

End Sub

Private Sub cmdForceLogoff_Click

ExitWindowsEx (EWX_LogOff Or EWX_FORCE), &HFFFF MsgBox "ExitWindowsEx's GetLastError " & GetLastError

End Sub

Private Sub cmdShutdown_Click

If glngWhichWindows32 = mlngWindowsNT Then AdjustToken MsgBox "Post-AdjustToken GetLastError " & GetLastError End If

ExitWindowsEx (EWX_SHUTDOWN), &HFFFF MsgBox "ExitWindowsEx's GetLastError " & GetLastError

End Sub

Private Sub cmdForceShutdown_Click If glngWhichWindows32 = mlngWindowsNT Then AdjustToken MsgBox "Post-AdjustToken GetLastError " & GetLastError End If

ExitWindowsEx (EWX_SHUTDOWN Or EWX_FORCE), &HFFFF MsgBox "ExitWindowsEx's GetLastError " & GetLastError

End Sub

Private Sub Form_Load '********************************************************************     '* When the project starts, check the operating system used by      '* calling the GetVersion function. '********************************************************************        Dim lngVersion As Long

lngVersion = GetVersion

If ((lngVersion And &H80000000) = 0) Then glngWhichWindows32 = mlngWindowsNT MsgBox "Running Windows NT or Windows 2000" Else glngWhichWindows32 = mlngWindows95 MsgBox "Running Windows 95/98/Me" End If

End Sub  To run the code:  In Visual Basic, run the project or compile to an EXE and run the EXE. In Access, open the form.</li>  In the other Office 97 applications, add a macro to show the UserForm: Sub ShowShutDownForm UserForm1.Show End Sub You can run this code from the Tools|Macro menu.

Also, in the UserForm, the last procedure's declaration needs to be changed from: Private Sub Form_Load to: Sub Form_Initialize </li> In Excel 95, you can assign the code to be run from a Dialog or from the Tools|Macro menu.</li></ul> </li></ol>