External for running one instance on windows

Trevor DeVore lists at mangomultimedia.com
Tue Jul 19 14:24:47 CDT 2005


On Jul 19, 2005, at 11:35 AM, Matthew wrote:

> There is another way to check if an instance is running that will  
> work on all OS. When you start the program you create a file if it  
> is not already there. If it is there then you close the program.
>
> I hope this helps.

Unfortunately you will run into problems if your application  
crashes.  The file will stay around and when you try to launch your  
app again it thinks it is already running.  You can come up with  
schemes to work around this but using a mutex is much more reliable  
and easier on Windows.  On Mac you don't have to worry about multiple  
instances for each user.  I don't do any Linux development right now  
so I can't comment on that.

The file method would work better if Revolution would allow you to  
get a lock on a file so that nobody else can access it.  I didn't see  
a way to do this with open file.  If this were the case then I think  
you could open the file and lock anybody else out from reading it.    
Then if another instance of your app launched and tried to open the  
file an error would be returned.  If the app crashed then I think the  
lock on the file would be released.


-- 
Trevor DeVore
Blue Mango Multimedia
trevor at mangomultimedia.com





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