Changing System Current Path from Console

Well, this is pretty tricky but you can do it on Windows 2000 and later, by using CreateRemoteThread and taking advantage of the fact that SetCurrentDirectory happens to have a signature compatible with that required of the thread entry point. Also, the Tool Help API provides the means to find the parent process. See below for some code that works for me. On systems earlier than Windows 2000 I think it is going to be tough to do without resorting to undocumented stuff.

DWORD GetParentProcessID()

{

    DWORD result = 0;

    HANDLE snap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);

    if (INVALID_HANDLE_VALUE != snap)

    {

        PROCESSENTRY32 entry = {sizeof(entry)};

        if (Process32First(snap, &entry))

        {

            DWORD pid = GetCurrentProcessId();

            do

            {

                if (pid == entry.th32ProcessID)

                {

                    result = entry.th32ParentProcessID;

                    break;

                }

            }

            while (Process32Next(snap, &entry));

        }

        CloseHandle(snap);

    }

    return result;

}

void SetCurrentDirectoryForProcess(HANDLE process, LPCTSTR dir)

{

    if (void * mem = VirtualAllocEx(process, 0,

        sizeof(TCHAR) * MAX_PATH, MEM_COMMIT, PAGE_READWRITE))

    {

        WriteProcessMemory(process, mem, dir, sizeof(TCHAR) * (lstrlen(dir) + 1), 0);

        if (HANDLE thread = CreateRemoteThread(process, 0, 0,

            LPTHREAD_START_ROUTINE(SetCurrentDirectory), mem, 0, 0))

        {

            WaitForSingleObject(thread, INFINITE);

            CloseHandle(thread);

        }

        VirtualFreeEx(process, mem, 0, MEM_RELEASE);

    }

}

void TestIt()

{

    if (DWORD pid = GetParentProcessID())

    {

        if (HANDLE hp = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid))

        {

            SetCurrentDirectoryForProcess(hp, _T("c:\\"));

            CloseHandle(hp);

        }

    }

}

--

Jim Barry, MVP for Windows SDK