Check if Windows-application is run as a service - winapi

Question

Is there a way to determine if a Windows-process is run as a service ? Is there any fixed parent-process of all the services which I can identify to assure that the process is a service-process.

Answer 1

if application designed for run both as service and as standalone application, the best way know how application started - use command line. when you register service with CreateServiceW - pass to lpBinaryPathName some arguments. and then on start - check string returned by GetCommandLineW() - are this arguments present. if yes - you run as service, if no - as standalone application.
for example append \n symbol to the service binary file path :
WCHAR BinaryPathName[MAX_PATH + 3];
ULONG cch = GetModuleFileNameW(0, BinaryPathName + 1, _countof(BinaryPathName) - 3);
if (GetLastError() == NOERROR)
{
BinaryPathName[0] = '\"';
BinaryPathName[cch + 1] = '\"';
BinaryPathName[cch + 2] = '\n';
BinaryPathName[cch + 3] = 0;
//CreateServiceW(.., BinaryPathName, ..);
}
(\n selected because this symbol can not be in command line if exec application manually )
and then in application entry point do very simply and fast check
if (wcschr(GetCommandLineW(), '\n'))
{
const static SERVICE_TABLE_ENTRY ste[] = { { L"my_service_name", ServiceMain }, {} };
StartServiceCtrlDispatcher(ste);
}
else
{
// run as standalone application
}
i think this solution is the best. however possible and others. for example we can do next check:
ULONG SessionId;
if (ProcessIdToSessionId(GetCurrentProcessId(), &SessionId) &&
WTSGetActiveConsoleSessionId() == SessionId)
{
// we not run as service;
}