Check user login using Windows API

main.cpp

// Complie with w64devkit:
// g++ main.cpp -o b -lWtsapi32

#define SECURITY_WIN32
#include <windows.h>
#include <Wtsapi32.h>
#include <iostream>

bool IsUserLoggedIn()
{
	WTS_SESSION_INFO *pSessionInfo = nullptr;
	DWORD sessionCount = 0;

	// Enumerate all sessions
	if (!WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE, 0, 1, &pSessionInfo, &sessionCount))
	{
		std::cerr << "Failed to enumerate sessions." << std::endl;
		return false;
	}

	bool userLoggedIn = false;

	// Iterate through all sessions to check if any are active
	for (DWORD i = 0; i < sessionCount; ++i)
	{
		if (pSessionInfo[i].State == WTSActive)
		{
			userLoggedIn = true;
			break; // Found an active user
		}
	}

	// Clean up
	if (pSessionInfo)
	{
		WTSFreeMemory(pSessionInfo);
	}

	return userLoggedIn;
}

int main()
{
	if (IsUserLoggedIn())
	{
		std::cout << "A user is logged in." << std::endl;
	}
	else
	{
		std::cout << "No user is logged in." << std::endl;
	}
	return 0;
}