Test if instance is already running.

[Tasp]

Hi all,

I'm looking to test to see if my program is already running and to prevent it from running a 2nd instance.

I'm sure I have done this before but I'm unsure how or where the code went!

I assume I need to check if the process is running. But I'm not sure where to even start looking for code to do that.

I've used the usual search terms I would associate with this but have drawn a blank.

Any ideas?

[Walt Decker]

User32.dll function GetWindowLong(WinHndl, GWL_HINSTANCE)

GWL_HINSTANCE = -6

PS:  On startup you could test for a simple text file.  If it is not present create it and continue; delete it at end of app.  If it is present, abort.

[Rod]

LBPE has this

alycesrestaurant.com/lbpe/MutEx.html

[Walt Decker]

Another possibility is User32.dll function EnumWindows(CallbackFunction Pointer, lParam)

The function enumerates all top-level windows on the screen by passing the handle of each window, in turn, to an application-defined callback function. EnumWindows continues until the last top-level window is enumerated or the callback function returns FALSE.

The callback function looks like:

FUNCTION EnumWindProc(hwnd, lParam)

WinName$ = SPACE$(180)

  CALLDLL #USER, "GetWindowText", hwnd AS ULONG, WinName$ AS PTR, 180 AS LONG, _

                      NumChrs AS LONG

WinName$ = LEFT$(NumChrs)

IF WinName$ = ThisProcName$ THEN EXIT FUNCTION

EnumWindProc = 1

END FUNCTION

[Tasp]

Thanks guys, I shall investigate both methods.

I didn't think of the txt file route and it does follow the KISS regime. However if the program crashes for any reason it could leave a text file there even after a restart.