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| Submitted on: |
4/28/1999 |
| By: |
Steve Pepper
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| Level: |
Not Given |
| User Rating: |
By 5 Users |
| Compatibility: |
VB 4.0 (32-bit), VB 5.0, VB 6.0 |
| Views: |
29998 |
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This code fragment demonstrates how you can get a program to change it's own priority.
Sometimes it is necessary to change the priority of a process from the default.
The example that prompted this code was a program I had to launch from a commercial scheduler always defaulted to idle priority. This caused the program to miss it's processing deadline. Increasing the priority to normal or high solved the problem.
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Windows API/Global Declarations: Can't Copy and Paste this?
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'**************************************
'Windows API/Global Declarations for :Changing priority
'**************************************
Option Explicit
Private Const NORMAL_PRIORITY_CLASS = &H20
Private Const IDLE_PRIORITY_CLASS = &H40
Private Const HIGH_PRIORITY_CLASS = &H80
Private Const REALTIME_PRIORITY_CLASS = &H100
Private Const PROCESS_DUP_HANDLE = &H40
Private Declare Function OpenProcess Lib "kernel32" (ByVal dwDesiredAccess As Long, _
ByVal bInheritHandle As Long, ByVal dwProcessId As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
Private Declare Function GetCurrentProcessId Lib "kernel32" () As Long
Private Declare Function SetPriorityClass& Lib "kernel32" (ByVal hProcess As Long, _
ByVal dwPriorityClass As Long)
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'**************************************
' Name: Changing priority
' Description:This code fragment demonstrates how you can get a program to change it's own priority.
Sometimes it is necessary to change the priority of a process from the default.
The example that prompted this code was a program I had to launch from a commercial scheduler always defaulted to idle priority. This caused the program to miss it's processing deadline. Increasing the priority to normal or high solved the problem.
' By: Steve Pepper
'
' Assumes:To run this code, add a form to a new project with a timer and a label.
The priority will toggle between idle and high every two seconds.
Under NT4, you can use the task manager to see the base priority of this process changing.
'
' Side Effects:Changing the priority of your process to REALTIME_PRIORITY_CLASS is a bad idea in Visual Basic.
I have only tested this code under NT4 sp4 and VB5 but I think it should work under Windows9x
'
'This code is copyrighted and has' limited warranties.Please see http://www.Planet-Source-Code.com/vb/scripts/ShowCode.asp?txtCodeId=1683&lngWId=1'for details.'**************************************
Sub ChangePriority(dwPriorityClass As Long)
Dim hProcess&
Dim ret&, pid&
pid = GetCurrentProcessId() ' get my proccess id
' get a handle to the process
hProcess = OpenProcess(PROCESS_DUP_HANDLE, True, pid)
If hProcess = 0 Then
Err.Raise 2, "ChangePriority", "Unable to open the source process"
Exit Sub
End If
' change the priority
ret = SetPriorityClass(hProcess, dwPriorityClass)
' Close the source process handle
Call CloseHandle(hProcess)
If ret = 0 Then
Err.Raise 4, "ChangePriority", "Unable to close source handle"
Exit Sub
End If
End Sub
Private Sub Form_Load()
Timer1.Interval = 2000
Call Timer1_Timer
End Sub
Private Sub Timer1_Timer()
Static Priority&
If Priority = IDLE_PRIORITY_CLASS Then
Priority = HIGH_PRIORITY_CLASS
Label1.Caption = "HIGH priority"
Else
Label1.Caption = "IDLE priority"
Priority = IDLE_PRIORITY_CLASS
End If
Call ChangePriority(Priority)
End Sub
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Other User Comments
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 5/2/1999 1:45:00 PM: Owen M
There is one program that can see if the priority has changed under Win 4x. It is Taskinfo98. You can download it at download.com(i think!)
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5/7/1999 9:17:00 PM: Andy M. Lopez
Thanks for the free source code, Thax's
I just want to learn more... :>
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5/11/1999 1:16:00 PM: 33
1
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11/2/1999 9:20:00 PM: Chan
do u know how to close other application like MS Access or Ms word?
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11/20/1999 9:33:00 AM: D
This code shows how powerful VB is and how easy it is to write powerful code. Changing the priority of a process programatically is powerful stuff and you showed how easy it can be done in VB. Thanks
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2/5/2000 5:51:19 AM: Bunzi
Fantastic Source-Code. Very useful, especially for security-tools.
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11/14/2000 5:01:08 PM: Dan Messenger
So wot will happen if i change the priority for ALL the processes so that they are all at the lowest priority ??
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1/5/2002 3:39:30 AM: Evil Monkey
sweet! 5 globes from me!
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7/1/2007 7:55:38 PM: vivalite
On my windows XP it gives #4 error.
However I've found a way around:
Public Declare Function GetCurrentProcess Lib "kernel32" () As Long
Public Declare Function SetPriorityClass Lib "kernel32" (ByVal hProcess As Long, ByVal dwPriorityClass As Long) As Long
Public Function ChangePriority(dwPriorityClass As Long)
Dim ret&
ret = SetPriorityClass(GetCurrentProcess, dwPriorityClass)
End Function
Where dwPriorityClass could be &H20 to &H100
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