WinAPI: How to enumerate processes?

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Q: How to enumerate currently running processes?

A: One method is by using Process Status API (PSAPI).

Example

#include <list>
#include <iostream>
#include <Windows.h>
#include <Psapi.h>
#pragma comment(lib, "Psapi.lib")
// Note: linking to Psapi.lib is not necessary if the target system is Windows 7 or newer

DWORD PSAPI_EnumProcesses(std::list<DWORD>& listProcessIDs, DWORD dwMaxProcessCount)
{
    DWORD dwRet = NO_ERROR;
    listProcessIDs.clear();
    DWORD *pProcessIds = new DWORD[dwMaxProcessCount];
    DWORD cb = dwMaxProcessCount * sizeof(DWORD);
    DWORD dwBytesReturned = 0;

    // call PSAPI EnumProcesses
    if (::EnumProcesses(pProcessIds, cb, &dwBytesReturned))
    {
        // push returned process IDs into the output list
        const int nSize = dwBytesReturned / sizeof(DWORD);
        for(int nIndex = 0; nIndex < nSize; nIndex++)
        {
            listProcessIDs.push_back(pProcessIds[nIndex]);
        }
    }
    else
    {
        dwRet = ::GetLastError();
    }
    delete[]pProcessIds;
    return dwRet;
}

int main()
{
    std::list<DWORD> listProcessIDs;
    const DWORD dwMaxProcessCount = 1024;
    DWORD dwRet = PSAPI_EnumProcesses(listProcessIDs, dwMaxProcessCount);
    if(NO_ERROR == dwRet)
    {
        const std::list<DWORD>::const_iterator end = listProcessIDs.end();
        std::list<DWORD>::const_iterator iter = listProcessIDs.begin();
        for( ; iter != end; ++iter)
        {
            DWORD dwProcessID = *iter;
            std::cout << "Process ID: " << dwProcessID << std::endl;
            // NOTE: you can pass dwProcessID to ::OpenProcess and further get
            // more process info by using the returned process handle 
        }
    }
    else
    {
        std::cout << "PSAPI_GetProcessesList failed. Error: " << dwRet << std::endl;
        return dwRet;
    }
    return 0;
}

Resources and related articles

• MSDN: Process Status API
• MSDN: EnumProcesses function
• Codexpert: Listing Processes – Part 2: Using PSAPI