HOWTO: List Running Processes

• Microsoft Visual Basic Professional and Enterprise Editions for Windows, versions 5.0, 6.0

SUMMARY

This article illustrates how you can list the processes that are currently running on a computer. The approach is different for Windows 95/98 and Windows NT; this article illustrates both solutions.

MORE INFORMATION

This situation requires that you first test to see which version of Windows is in use. Once that determination is made, the correct code can then be run to examine and list the current processes. On Windows NT, requests for information on some system processes may be denied for security or other related reasons. The approach taken in this article will ignore any process that cannot be accessed.

PSAPI.DLL is the library used to gather process information on Windows NT and must reside in the \SYSTEM32 directory. There are two versions of this file, 3.51 and 4.0. Either version will work for this example, but using the most recent version is recommended. If you have installed the Windows NT 4.0 Resource Kit or the Windows NT 4.0 SDK, this file will be present on your computer. The 4.0 version of the file is available on the Visual Studio Visual C++ CD-ROM in the following directory:

\DEVSTUDIO\VC\BIN\PSAPI.DLL.

\TOOLS\UNSUPPRT\WSVIEW\WINNT\PSAPI.DLL

Step-by-Step Example

1. Create a new Standard Exe project in Visual Basic. Form1 is created by default.



2. Add a CommandButton to Form1.



3. Add a ListBox to Form1.



4. Copy the following code to Form1:
   

   
         Option Explicit
   
         Private Sub Command1_Click()
         List1.Clear
         Select Case getVersion()
   
         Case 1 'Windows 95/98
   
            Dim f As Long, sname As String
            Dim hSnap As Long, proc As PROCESSENTRY32
            hSnap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0)
            If hSnap = hNull Then Exit Sub
            proc.dwSize = Len(proc)
            ' Iterate through the processes
            f = Process32First(hSnap, proc)
            Do While f
              sname = StrZToStr(proc.szExeFile)
              List1.AddItem sname
              f = Process32Next(hSnap, proc)
            Loop
   
         Case 2 'Windows NT
   
            Dim cb As Long
            Dim cbNeeded As Long
            Dim NumElements As Long
            Dim ProcessIDs() As Long
            Dim cbNeeded2 As Long
            Dim NumElements2 As Long
            Dim Modules(1 To 200) As Long
            Dim lRet As Long
            Dim ModuleName As String
            Dim nSize As Long
            Dim hProcess As Long
            Dim i As Long
            'Get the array containing the process id's for each process object
            cb = 8
            cbNeeded = 96
            Do While cb <= cbNeeded
               cb = cb * 2
               ReDim ProcessIDs(cb / 4) As Long
               lRet = EnumProcesses(ProcessIDs(1), cb, cbNeeded)
            Loop
            NumElements = cbNeeded / 4
   
            For i = 1 To NumElements
               'Get a handle to the Process
               hProcess = OpenProcess(PROCESS_QUERY_INFORMATION _
                  Or PROCESS_VM_READ, 0, ProcessIDs(i))
               'Got a Process handle
               If hProcess <> 0 Then
                   'Get an array of the module handles for the specified
                   'process
                   lRet = EnumProcessModules(hProcess, Modules(1), 200, _
                                                cbNeeded2)
                   'If the Module Array is retrieved, Get the ModuleFileName
                   If lRet <> 0 Then
                      ModuleName = Space(MAX_PATH)
                      nSize = 500
                      lRet = GetModuleFileNameExA(hProcess, Modules(1), _
                                      ModuleName, nSize)
                      List1.AddItem Left(ModuleName, lRet)
                   End If
               End If
             'Close the handle to the process
            lRet = CloseHandle(hProcess)
            Next
   
         End Select
         End Sub
    




5. Add a Standard Module to the Project. Module1 is created.



6. Paste the following code into Module1.
   

   
         Public Declare Function Process32First Lib "kernel32" ( _
            ByVal hSnapshot As Long, lppe As PROCESSENTRY32) As Long
   
         Public Declare Function Process32Next Lib "kernel32" ( _
            ByVal hSnapshot As Long, lppe As PROCESSENTRY32) As Long
   
         Public Declare Function CloseHandle Lib "Kernel32.dll" _
            (ByVal Handle As Long) As Long
   
         Public Declare Function OpenProcess Lib "Kernel32.dll" _
           (ByVal dwDesiredAccessas As Long, ByVal bInheritHandle As Long, _
               ByVal dwProcId As Long) As Long
   
         Public Declare Function EnumProcesses Lib "psapi.dll" _
            (ByRef lpidProcess As Long, ByVal cb As Long, _
               ByRef cbNeeded As Long) As Long
   
         Public Declare Function GetModuleFileNameExA Lib "psapi.dll" _
            (ByVal hProcess As Long, ByVal hModule As Long, _
               ByVal ModuleName As String, ByVal nSize As Long) As Long
   
         Public Declare Function EnumProcessModules Lib "psapi.dll" _
            (ByVal hProcess As Long, ByRef lphModule As Long, _
               ByVal cb As Long, ByRef cbNeeded As Long) As Long
   
         Public Declare Function CreateToolhelp32Snapshot Lib "kernel32" ( _
            ByVal dwFlags As Long, ByVal th32ProcessID As Long) As Long
   
         Public Declare Function GetVersionExA Lib "kernel32" _
            (lpVersionInformation As OSVERSIONINFO) As Integer
   
         Public Type PROCESSENTRY32
            dwSize As Long
            cntUsage As Long
            th32ProcessID As Long           ' This process
            th32DefaultHeapID As Long
            th32ModuleID As Long            ' Associated exe
            cntThreads As Long
            th32ParentProcessID As Long     ' This process's parent process
            pcPriClassBase As Long          ' Base priority of process threads
            dwFlags As Long
            szExeFile As String * 260       ' MAX_PATH
         End Type
   
         Public Type OSVERSIONINFO
            dwOSVersionInfoSize As Long
            dwMajorVersion As Long
            dwMinorVersion As Long
            dwBuildNumber As Long
            dwPlatformId As Long           '1 = Windows 95.
                                           '2 = Windows NT
   
            szCSDVersion As String * 128
         End Type
   
         Public Const PROCESS_QUERY_INFORMATION = 1024
         Public Const PROCESS_VM_READ = 16
         Public Const MAX_PATH = 260
         Public Const STANDARD_RIGHTS_REQUIRED = &HF0000
         Public Const SYNCHRONIZE = &H100000
         'STANDARD_RIGHTS_REQUIRED Or SYNCHRONIZE Or &HFFF
         Public Const PROCESS_ALL_ACCESS = &H1F0FFF
         Public Const TH32CS_SNAPPROCESS = &H2&
         Public Const hNull = 0
   
         Function StrZToStr(s As String) As String
            StrZToStr = Left$(s, Len(s) - 1)
         End Function
   
         Public Function getVersion() As Long
            Dim osinfo As OSVERSIONINFO
            Dim retvalue As Integer
            osinfo.dwOSVersionInfoSize = 148
            osinfo.szCSDVersion = Space$(128)
            retvalue = GetVersionExA(osinfo)
            getVersion = osinfo.dwPlatformId
         End Function
    




7. Run the project and click the Command button on Form1. You should see a listing of the currently running processes.



8. If you are running Windows 95/98, try running the example project on Windows NT or vice versa. The processes should be listed regardless of operating system version.

REFERENCES

Portions of the code in this article were adapted from "Hardcore Visual Basic" Second Edition by Bruce McKinney - Microsoft Press

For additional information on the GetVersionExA API, please see the following article in the Microsoft Knowledge Base:

Q189249 : HOWTO: Determine Which 32-bit Operating System Is Being Used

Additional query words: kbAPI kbVBp500 kbVBp kbPSAPI kbSDKWin32 kbVBp600 toolhelp

Keywords : kbAPI kbPSAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600
Version :
Platform : WINDOWS
Issue type : kbhowto