From: "Earl F. Glynn"
Newsgroups: borland.public.delphi.winapi
References: <3acb37a2$1_2@dnews>
Subject: Re: How do I make sure only one copy of exe is running?
Date: Wed, 4 Apr 2001 11:17:15 -0500
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"John Bouris" <jbouris@ziplink.net> wrote in message news:3acb37a2$1_2@dnews...
> I know I've seen this tip somewhere but I can't find it.
>
> I want to stop the user from starting a second copy of my exe.

Place the following in the project (.DPR) file:
VAR
  MutexHandle:  THandle;

begin
  // Use Mutex to only allow one copy of XXXXX to be in memory at a time
  MutexHandle := 0;

  TRY
    MutexHandle := CreateMutex(NIL, TRUE, 'TFormXXXXX);
    IF   GetLastError = ERROR_ALREADY_EXISTS
    THEN BEGIN
      SetForegroundWindow(FindWindow('TFormXXXXX', NIL));
      CloseHandle (MutexHandle)
    END
    ELSE BEGIN
      Application.Title := 'XXXXX';
      Application.CreateForm(TFormXXXXX, FormXXXXX);
...
      Application.Run;
    END
  FINALLY
    ReleaseMutex(MutexHandle)
  END
end.

In several Delphi PC Magazine utilities, Neil Rubenking uses a different approach.  Here's how Neil
prevented two instances of his recent KeyClick utility from running:

TYPE
  THandles = Record
    AppHandle : HWnd;
    WinHandle : HWnd;
  end;
VAR
  hMap : THandle;
  PH   : ^THandles;
begin
  hMap := OpenFileMapping(FILE_MAP_ALL_ACCESS, False, MainMapName);
  IF hMap = 0 THEN // first instance
    begin
      hMap := CreateFileMapping($FFFFFFFF, NIL, PAGE_READWRITE, 0,
        SizeOf(THandles), MainMapName);
      PH := MapViewOfFile(hMap, FILE_MAP_ALL_ACCESS, 0, 0, 0);
      Application.Initialize;
      Application.Title := 'KeyTick';
      Application.CreateForm(TMainForm, MainForm);
  Application.MainForm.HandleNeeded;
      PH^.AppHandle := Application.Handle;
      PH^.WinHandle := Application.Mainform.Handle;
      Application.Run;
    end
  ELSE
    begin
      PH := MapViewOfFile(hMap, FILE_MAP_ALL_ACCESS, 0, 0, 0);
      SendMessage(PH^.WinHandle, regMsg, -1, -1);
    end;
  UnMapViewOfFile(PH);
  CloseHandle(hMap);
end.

In case you're interested, find complete source code for Neil's KeyClick here:
http://www.zdnet.com/pcmag/stories/solutions/0,8224,2692946,00.html

Or, look at any of Neil's other Delphi utilities by searching from that page.


--
efg     efg2@efg2.com     Earl F. Glynn, Overland Park, KS  USA

efg's Computer Lab:  http://www.efg2.com/Lab
Mirror:  http://homepages.borland.com/efg2lab/Default.htm