Excellent approach and very standard. I would also think that the poster would want to install a signal handler(s) to release appropriate locks if the program dies, get's a CTL-C or whatever. Something like this: 
$SIG{'INT'} =  \&release_lock;
$SIG{'QUIT'} = \&release_lock;
$SIG{'PIPE'} = \&release_lock; #maybe too?

sub release_lock{
#...do what you can here...
}

[download]

The basic idea is not to leave locks around if your program abends. The lock strategy is simple, works well, and can be implemented in many languages on many O/s'es (some easier than others)..just remember to clean up if "bad things" happen to your program and the normal "release lock" code doesn't execute.

The lock system is cooperative, meaning that everybody has to know what is going on and cooperate. It is possible to write a file that is "locked" for exclusive access. A file lock is more like an advisory thing and the programs that use it have to "play by the rules".

In reply to Re^2: Abort if instance already running? by Marshall
in thread Abort if instance already running? by pileofrogs

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