The information in this article applies to:
- Microsoft Visual Basic Control Creation, Learning, Professional and
Enterprise Editions for Windows, version 5.0
on the following platform: x86
- Microsoft Visual Basic Standard, Professional, and Enterprise Editions,
32-bit only, for Windows, version 4.0
- Microsoft Access versions 7.0, 97
- Microsoft Excel 97 for Windows
- Microsoft Excel for Windows 95, version 7.0
- Microsoft Word 97 for Windows
- Microsoft PowerPoint 97 for Windows
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 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, enable the SE_SHUTDOWN_NAME security
privilege by using the AdjustTokenPrivileges function. Windows 95 does 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:
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:
- Log Off - calls the ExitWindowsEx function with the EWX_Logoff flag to
log off the user. The user can shut down all running programs.
- Forced Log off - calls the ExitWindowsEx function with the EWX_Logoff or
the EWX_Forced flags to initiate a forced log off.
- Shut Down - if the operating system is Windows NT, 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.
- Forced Shut Down - if the operating system is Windows NT, 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"
Else
glngWhichWindows32 = mlngWindows95
MsgBox "Running Windows 95"
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.
- 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()
In Excel 95, you can assign the code to be run from a Dialog or from the
Tools|Macro menu.
Notes
If you aren't implementing the code on a form, the code contained in the
Form_Load must be run prior to the other code.
Make sure you have saved all running programs before clicking a command
button.
In Windows 95, your application may remain visible when executing the
logoff and force logoff code. You may want to close your application after
the API call returns. This is not a problem with the shutdown or force
shutdown code.
REFERENCES
Win32 Programmer's Reference-Search on the following topics:
- AdjustTokenPrivileges
- ExitWindowsEx
- GetLastError
- Privileges
- Logging Off or Shutting Down
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