On Jan 30, 2005, at 12:58 PM, Aaron Ballman wrote:
Sorta. You make a named mutex which is a system-wide object that
any application can access. You then obtain the mutex (much the
same way you would Enter a critical section or Signal a semaphore).
If you aren't able to obtain a lock on the mutex, then you know some
other instance of your application is running on the same machine.
There's no hand-off involved -- it's just another type of locking
mechanism.
OK ...
Suppose that an instance of this app is already running and a second
instance is started to open another document.
If there's no hand off to get the first running instance to open that
document that the the new second instance should have the second
simply dies when it sees that there is already one running and the
document is not opened.
Mutexes have next-to-nothing to do with the above scenario (aside from
the obvious detection of the second application running).
If you want to handle the above situation, then you should use an
IPCSocket to tell the other application which document to open (though
any communication mechanism will work, such as TCPSocket, AppleEvents
[on the Mac, obviously] or even UDPSockets).
Right ... that's why I originally said use a mutex to detect that an
instance is already running "and then hand it off to the other instance
(that I'm not sure how you do ....)"
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