Hi Perl monks. I have a large program with many different packages. Some of the packages use voluntary file locks, that are normally cleaned out in the END block. But, when a SIGINT is sent, the END block doesn't get seen. So I had the idea to "chain" signal handlers on SIGINT:

# Use a closure to add a new behavior to the 
# chain of behavior for the interupt handler
{
my $OldINTHandler = $SIG{'INT'};
defined $OldINTHandler or $OldINTHandler = sub { exit(2); };
sub NewIntHandler {
    unlink(@LockFileArray);
    &{$OldINTHandler};
    }
# Install the new handler
$SIG{'INT'} = \&NewIntHandler;
}

[download]


The idea here is to preserve any existing behavior but still unlink my file locks in the case of a SIGINT. I think that me implementation is solid can be used throughout. However, signal handlers can have unexpected behavior -- and I would really like to hear what might go wrong with this approach. (Assuming the chaining method is used throughout - ie, $SIG{'INT'} isn't stupidly set to a non-chaining handler.)

One point of concern -- I couldn't find a code reference to the default handler, so I had to put an 'exit' in explicitly. Maybe you know a better way?

BTW - I know there are many more signals.. at most I would catch SIGTERM too, so 'kill' would work in a nice way.

Thanks for your help!

In reply to Chaining Signal Handlers by Anonymous Monk

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