Detect multiple run

Is there a way to detect if my program is already running ?

I don't want to create a file on the hard disk or anything like that (someone already told me to try that but it's not working everytime as expected).

MagicalTux

Found that :
http://www.blitzbasic.com/Community/posts.php?topic=21457

but it *must* be another way ... checking running processes etc...

I know it can be done through the Windows API, but I don't remember which ones.

You could do a 'FindWindow' on you own title bar. So you run, change your own app title to 'I am a Wombat' or something. Then do a FindWindow for 'WhizzyGame'. If you find it, then you are already running and will exit.

Otherwise, set your apptitle to 'WhizzyGame' and continue.

I think this is the FindWindowAPI call...

.lib "user32.dll"
 
FindWindow%( class$,Text$ ):"FindWindowA"

Another way is to create a mutex each time you start your application. If the mutex is already opened, the application is already running.

I tried this:

.lib "kernel32.dll"

CreateMutex%(lpMutexAttributes*,bInitialOwner,lpName$):"CreateMutexA" 
GetLastError%():"GetLastError"

Const ERROR_ALREADY_EXISTS=183

mutex$="Choose_something"
attributes=CreateBank(4)
PokeInt attributes,0,0

mutex_h=CreateMutex(attributes,1,mutex$)
FreeBank(attributes)

If GetLastError() <> ERROR_ALREADY_EXISTS
 Print "1st time."
Else
 Print "Already running."
EndIf

Input 
End

It's a better way than FindWindow, but sadly it does not work. I always get an ERROR_INVALID_PARAMETER from GetLastError. I guess the problem is that the 2nd parameter must a BOOL (a byte) , is it possible to pass a byte to a DLL under Blitz ?

Sending in a bank with the value of 0 is not the same as sending in NULL.

Notice that in the userlib declaration, I changed the lpMutexAttributes paramter to be an int%, not a pointer*.

.lib "Kernel32.dll"
CreateMutex%(lpMutexAttributes%,bInitialOwner%,lpName$):"CreateMutexA" 
GetLastError%():"GetLastError"

And the simple example code:

Const ERROR_ALREADY_EXISTS=183

CreateMutex(0,1,"My Program Instance") ; Mutex accessible to any program

If GetLastError() = ERROR_ALREADY_EXISTS Then
	Notify "My program is already running" ; Shutdown
Else
	Notify "This is the only instance of My Program" ; OK
EndIf

Thanks for the idea, it works great.

Ah, that was the problem. Thanks soja.

Neat!