// global function:
HWND GetRunningWindow() {
	// Check if exists an application with the same TITLE as this application
	HWND hWnd = FindWindow(NULL, "My TopWindow Title");
	if (IsWindow(hWnd))	{
		HWND hWndPopup = GetLastActivePopup(hWnd);
		if (IsWindow(hWndPopup))
		hWnd = hWndPopup; // Previous instance exists
	} else {
		hWnd = NULL; // Previous instance doesnt exist
	}
	return hWnd;
}

GUI_APP_MAIN
{
	// Checks for previous instance of our app
	HWND hOtherWnd = GetRunningWindow();
	// Allow only one app instance
	if (hOtherWnd) {// hOtherWnd != NULL -> Previous instance exists
		PromptOK("The program is already running");
		SetForegroundWindow(hOtherWnd); // Activate it &
		if (IsIconic(hOtherWnd))
			ShowWindow(hOtherWnd, SW_RESTORE); // restore it
		return; // Abort current app execution
	}
	
// ... otherwise, run app here ...

}

//at beginning of your programm#define SEMAPHORE_UNIQUE "Global\\LIPANv2Unique_2FA34E51"


#ifdef SINGLE_APPINSTANCE
#ifdef PLATFORM_WIN32
	USemh = OpenSemaphore(STANDARD_RIGHTS_ALL, FALSE, SEMAPHORE_UNIQUE);
	if(USemh == NULL)
		USemh = CreateSemaphore(NULL, 0, 1, SEMAPHORE_UNIQUE);
	else
	{
		wq & THISBACK1(Closer, "Application already started!!"); //prepare
		return;
	}
#elif defined(PLATFORM_POSIX)
#endif
#endif

//program runtime....


//at end of your program
#ifdef SINGLE_APPINSTANCE
#ifdef PLATFORM_WIN32
	if(USemh != NULL)
		CloseHandle(USemh);
	USemh = NULL;
#elif defined(PLATFORM_POSIX)
#endif
#endif

bool QSkillsWin::IsSingleInstance()
{
    if(GetWindowIdFromCaption(GetTitle().ToString())>0)return true;
	  else return false;
}

GUI_APP_MAIN
{
	SetLanguage(GetSystemLNG());
	SetLNGCharset(GetSystemLNG(),CHARSET_UTF8);
	
	if(QSkillsWin().IsSingleInstance())
	{
		Exclamation("[=*A4@5 "+DeQtfLf(t_("QSkills s'exécute déjà !"))+"]");
		return;
	}
	 else QSkillsWin().Run();
}

void ChangeStatus() {
	SaveFile(GetExeDirFile("lock"), "Finished succesfully");
}

if(!FileExists(GetExeDirFile("lock")))
	   SaveFile(GetExeDirFile("lock"), "Finished sucessfully");
	   
	String status = LoadFile(GetExeDirFile("lock"));
	
	if(status == "running")
	{
		Exclamation("There's another instance!");
		return;
	}
	
	if(status == "crashed") {
		Exclamation("The program crashed on the last run. Please restart the application.");
		RecoverData();
		ChangeStatus();
		return;
	}
	
	SaveFile(GetExeDirFile("lock"), "running");
	
	atexit(ChangeStatus);

SaveFile(GetExeDirFile("lock"), "crashed");
DoLongOperations(); // if it crashes now we're safe
SaveFile(GetExeDirFile("lock"), "running"); // We survived