Limit applications to one instance in Visual C++

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Introduction

Sometimes you need to limit your application to a single instance. The most common way is creating a named mutex using CreateMutex, and checking to see if that mutex already existed or not.  If that mutex already exists, it means that another instance application reside in your computer memory so you can kill your current instance.

How to use this code

#pragma once class CSingleInstance { private: DWORD dwLastError; HANDLE hMutexHandle; public: CSingleInstance(char *mutexNameStr) { hMutexHandle = CreateMutex(NULL, FALSE, mutexNameStr); dwLastError = GetLastError(); } ~CSingleInstance(void) { if(hMutexHandle) { CloseHandle(hMutexHandle); hMutexHandle = NULL; } } BOOL isAtnotherInstanceRunning() { return (dwLastError == ERROR_ALREADY_EXISTS); } };

All you need to do is to create a global instance of the CSingleInstance class before the entry point function. If this is being used in a MFC application, create the instance before the InitInstance() function.

BOOL isAtnotherInstanceRunning() – return TRUE if another instance already exists and FALSE if not.

License

This article, along with any associated source code and files, is licensed under The Intelliproject Open License (IPOL)

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