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Only one application instance allowed?

Started by Impz0r Aug 17, 2006 at 5:45 AM 1 replies 500+ views

Original Post

Aug 17, 2006 at 5:45 AM

Heya, as the topic says, i'm trying to restrict my application to only run once. Meaning i only want one instance running at a time. To achieve this, i'm using a Mutex as the following:


HANDLE hMutex = ::CreateMutex (NULL, True, "Global\\MyVeryOwnInstanceName");
if (hMutex)
 {
  if (::GetLastError () == ERROR_ALREADY_EXISTS)
   {
    ::CloseHandle (hMutex);
    throw "Only one instance allowed.";
   }
  else
   ::CloseHandle (hMutex);
 }

But this wont work for me, GetLastError () never returns ERROR_ALREADY_EXISTS regardless how many instances allready running. Any ideas ? Impz0r

DaBono

Aug 17, 2006 at 5:56 AM

By closing the handle, you release the mutex immediately after checking if there is another instance running. However, you need to hold on to that handle during the entire course of the program.
(Also, I think you need to lose the 'if(hMutex)'-check.)

Impz0r

Aug 17, 2006 at 6:40 AM

I'm with stupid!

You're absolutely right DaBono, i need to hold the Mutex handle and not to destroy it right after i created it ...

Thanks DaBono!

Impz0r

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