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RunOnlyOnce: via Mutex.

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Submitted on: 1/1/2015 8:54:00 AM
By: David Ward (from psc cd)  
Level: Beginner
User Rating: By 2 Users
Compatibility: Delphi 5, Delphi 4, Pre Delphi 4
Views: 1376
 
     Code: Another, different, RunOnlyOnce solution.
 
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!**************************************
! Name: RunOnlyOnce: via Mutex.
! Description:Code: Another, different, RunOnlyOnce solution.
! By: David Ward (from psc cd)
!**************************************

So here it is then, a 3 step process.
[1] Put the following function declaration in the INTERFACE section of any unit of your project,
immediately prior to the IMPLEMENTATION section header;
Function AlreadyRunning: Boolean;
[2] and the following function in the IMPLEMENTATION section of that same unit;
Function AlreadyRunning: Boolean;
Var
MutexHandle: THandle;
Begin
 Result:=False; 
 MutexHandle:=CreateMutex(nil,TRUE,'NameofMyProgram-version1.2.3'); 
 // 'NameofMyProgram-version1.2.3' can be any text string, it just needs to be unique to each program. 
 If MutexHandle<>0 then
 If GetLastError=ERROR_ALREADY_EXISTS then
Result:=True; // Yes, this Mutex does already exist, this program is already running!
end; 
[3] Finally, in your Project source file (the .DPR) in the main "Begin ... End." clause do this;
Begin // existing line
 If not AlreadyRunning then
 begin
// inside here will be ALL the existing code that already was in the main "Begin ... End." clause.
 end;
End. // existing line


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