Fixed lock file for Mac

Author: mrbindraw

Source/CheckAppInstance/Private/CheckAppInstanceBPLibrary.cpp

@@ -3,6 +3,8 @@
 #include "CheckAppInstanceBPLibrary.h"
 #include "CheckAppInstance.h"
 
+DEFINE_LOG_CATEGORY(LogCheckAppInstanceBPLibrary)
+
 UCheckAppInstanceBPLibrary::UCheckAppInstanceBPLibrary(const FObjectInitializer& ObjectInitializer)
 : Super(ObjectInitializer)
 {
@@ -18,17 +20,41 @@ void UCheckAppInstanceBPLibrary::CheckAnotherAppInstance(bool bIsEnabled)
 		bIsEnabled = ParseValue.ToBool();
 	}
 
+	if(!bIsEnabled)
+	{
+		return;
+	}
+
 	FCoreDelegates::OnAllModuleLoadingPhasesComplete.AddLambda([bIsEnabled]() 
 	{	
 		// Only one instance of the game can be initialized!
 		const UGeneralProjectSettings& ProjectSettings = *GetDefault<UGeneralProjectSettings>();
 		const FString LockFilePath = FPlatformProcess::UserTempDir() + ProjectSettings.ProjectID.ToString();
-		if (!IFileManager::Get().CreateFileWriter(*LockFilePath, 0) && bIsEnabled)
+		bool bIsAppInstLaunched = false;
+
+#if PLATFORM_WINDOWS
+		bIsAppInstLaunched = (IFileManager::Get().CreateFileWriter(*LockFilePath, 0) == nullptr ? true : false);
+#else
+		int FileDescriptor = open(TCHAR_TO_UTF8(*LockFilePath), O_CREAT | O_RDWR, 0666); // 0644
+		if(FileDescriptor >= 0)
+		{
+			int CodeFlock = flock(FileDescriptor, LOCK_EX | LOCK_NB);
+			if (CodeFlock && errno == EWOULDBLOCK)
+			{
+				flock(FileDescriptor, LOCK_UN);
+				close(FileDescriptor);
+
+				bIsAppInstLaunched = true;
+			}
+		}
+#endif
+		UE_LOG(LogCheckAppInstanceBPLibrary, Log, TEXT("LockFilePath: %s, bIsAppInstLaunched: %s"), *LockFilePath, bIsAppInstLaunched ? TEXT("true") : TEXT("false"));
+		if (bIsAppInstLaunched)
 		{
 			FPlatformApplicationMisc::RequestMinimize();
 			FPlatformMisc::RequestExit(0);
 		}
 	});
-#endif
+#endif // !UE_EDITOR
 }
 

Source/CheckAppInstance/Public/CheckAppInstanceBPLibrary.h

@@ -8,8 +8,18 @@
 #include "GeneralProjectSettings.h"
 #include "Misc/CoreDelegates.h"
 #include "Misc/CommandLine.h"
+
+#if PLATFORM_UNIX
+#include <unistd.h>		// close
+#include <fcntl.h>		// open
+#include <sys/file.h>	// flock
+#include <errno.h>
+#endif
+
 #include "CheckAppInstanceBPLibrary.generated.h"
 
+DECLARE_LOG_CATEGORY_EXTERN(LogCheckAppInstanceBPLibrary, Log, All);
+
 UCLASS()
 class UCheckAppInstanceBPLibrary : public UBlueprintFunctionLibrary
 {