How can I limit my application to one instance?

[Ness]

[Andreas]: The following question was asked in regard to the following FAQ: Application: How can I limit my application to one instance? (http://www.codeguru.com/forum/showthread.php?s=&threadid=231178)...



How would you go about doing it with Win32?

[Andreas Masur]

Basically the same way...the code shown in the FAQ for protecting multiple instances of your application itself uses already a standard Win32 API function...the only difference would be the place where you do it...in an application different than a MFC one it would be 'main()'/'WinMain()' instead...

[hephaestusp]

bool isRunning = FALSE ;

isRunning = FindWindow( szClassName , hName);
if ( isRunning )
{
return 0;
}

Where "szClassName" is a char array, string, which contains the name of your main window. The easier way I have found to do this. You might even try to replace the "return 0" line with a message window notifing you for what you want.

[Bond]

Another:

BOOL IsAlreadyRunning()
{
HANDLE hMutex = CreateMutex(NULL, TRUE, g_szAppName);
BOOL bAlreadyRunning = (GetLastError() == ERROR_ALREADY_EXISTS);
ReleaseMutex(hMutex);

return bAlreadyRunning;
}

[Andreas Masur]

bool isRunning = FALSE ;

isRunning = FindWindow( szClassName , hName);
if ( isRunning )
{
return 0;
}

Where "szClassName" is a char array, string, which contains the name of your main window. The easier way I have found to do this. You might even try to replace the "return 0" line with a message window notifing you for what you want.
Well....the above method has some drawbacks and thus is not reliable...

[Andreas Masur]

Another:

BOOL IsAlreadyRunning()
{
HANDLE hMutex = CreateMutex(NULL, TRUE, g_szAppName);
BOOL bAlreadyRunning = (GetLastError() == ERROR_ALREADY_EXISTS);
ReleaseMutex(hMutex);

return bAlreadyRunning;
}

Which is the way shown in the FAQ...