[Tips] Get all ProcessID on Operation System By CreateToolhelp32Snapshot API

In C++, you can easy to get all ProcessID on Operation System.By using PROCESSENTRY32, CreateToolhelp32Snapshot, Process32First API.

Now let's take a look

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CreateToolhelp32Snapshot

HANDLE WINAPI CreateToolhelp32Snapshot(
  _In_ DWORD dwFlags,
  _In_ DWORD th32ProcessID
);

Parameters

dwFlags [in] 
       The portions of the system to be included in the snapshot. This parameter can be one or more of the following values.
   + TH32CS_INHERIT
   + TH32CS_SNAPALL
   + TH32CS_SNAPHEAPLIST
   + TH32CS_SNAPMODULE
   + TH32CS_SNAPMODULE32
   + TH32CS_SNAPPROCESS
   + TH32CS_SNAPTHREAD

th32ProcessID [in]

The process identifier of the process to be included in the snapshot. This parameter can be zero to indicate the current process. This parameter is used when the TH32CS_SNAPHEAPLIST, TH32CS_SNAPMODULE, TH32CS_SNAPMODULE32, or TH32CS_SNAPALL value is specified. Otherwise, it is ignored and all processes are included in the snapshot.

If the specified process is the Idle process or one of the CSRSS processes, this function fails and the last error code is ERROR_ACCESS_DENIED because their access restrictions prevent user-level code from opening them.

If the specified process is a 64-bit process and the caller is a 32-bit process, this function fails and the last error code is ERROR_PARTIAL_COPY (299).

Return Value

If the function succeeds, it returns an open handle to the specified snapshot.
If the function fails, it returns INVALID_HANDLE_VALUE. To get extended error information, call GetLastError. Possible error codes include ERROR_BAD_LENGTH.

Process32First

BOOL WINAPI Process32First(
  _In_    HANDLE           hSnapshot,
  _Inout_ LPPROCESSENTRY32 lppe
);

Parameters

hSnapshot [in]

A handle to the snapshot returned from a previous call to the CreateToolhelp32Snapshot function.

lppe [in, out]

A pointer to a PROCESSENTRY32 structure. It contains process information such as the name of the executable file, the process identifier, and the process identifier of the parent process.

Return value

Returns TRUE if the first entry of the process list has been copied to the buffer or FALSE otherwise. The ERROR_NO_MORE_FILES error value is returned by the GetLastError function if no processes exist or the snapshot does not contain process information.

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Remarks

The calling application must set the dwSize member of PROCESSENTRY32 to the size, in bytes, of the structure.

To retrieve information about other processes recorded in the same snapshot, use the Process32Next function.

Source code Example:

This program will be Read All Process and get Skype process name
 

/********************************************************************************
Developer: zidane (huuvi168@gmail.com)
Last Modified: 2013-09-01
 ********************************************************************************/
#include "stdafx.h"
#include <tlhelp32.h>

/* -----------------------------------------------------------------------
  compare path with skype.exe, if equal, return true, otherwise return false
   --------------------------------------------------------------------- */
bool CTestDlg::CheckProcess(const wchar_t* path)
{
    if ( wcscmp(path, L"skype.exe")==0 || wcscmp(path, L"skype.exe *32")==0 || 
         wcscmp(path, L"Skype.exe")==0 ||wcscmp(path, L"Skype.exe *32")==0 )
 return true;
 
    return false;
}

/* -----------------------------------------------------------------------
  Browser All Process On OS, get process Id with Skype.exe file name 
  and get Handle of Skype ProcessID
   --------------------------------------------------------------------- */
void CTestDlg::GetAnyProcess()
{
    PROCESSENTRY32 entry;
    entry.dwSize = sizeof(PROCESSENTRY32);

    HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, NULL);
 
    if (Process32First(snapshot, &entry) == TRUE)
    {  
        do
        {  
            if (CheckProcess(entry.szExeFile) == 1)
            {  
                // do something here...
                HANDLE hHandle = OpenProcess(PROCESS_ALL_ACCESS, FALSE, 
                                       entry.th32ProcessID);
                CString szMsg = L"";
                szMsg.Format(L"entry.th32ProcessID = 0x%08X(%d) 
     - hHandle = 0x%08X", entry.th32ProcessID, entry.th32ProcessID, hHandle);
                MessageBox(szMsg);   
            }   
        } while (Process32Next(snapshot, &entry) == TRUE);
    }

    CloseHandle(snapshot);
}

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