Question

When you use exec() in Perl:

Note that exec will not call your END blocks, nor will it invoke DESTROY methods on your objects.

How do I force perl to call END blocks anyway? Can I do something like END(); exec($0) or whatever?

I really am trying to make the program end its current instance and start a brand new instance of itself, and am too lazy to do this correctly (using cron or putting the entire program in an infinite loop). However, my END subroutines cleanup temp files and other important things, so I need them to run between executions.

Unhelpful links to code:

https://github.com/barrycarter/bcapps/blob/master/bc-metar-db.pl

https://github.com/barrycarter/bcapps/blob/master/bc-voronoi-temperature.pl

https://github.com/barrycarter/bcapps/blob/master/bc-delaunay-temperature.pl

Answer 1

To answer the narrow question of how to invoke your END blocks at arbitrary times, you can use the B::end_av method with B::SV::object_2svref to get the code references to your END blocks.

sub invoke_end_blocks_before_exec {
    use B;
    my @ENDS = B::end_av->ARRAY;
    foreach my $END (@ENDS) {
        $END->object_2svref->();
    }
}

END { print "END BLOCK 1\n" }
END { print "END BLOCK 2\n" }

...

invoke_end_blocks_before_exec();
exec("echo leave this program and never come back");

---

Output:

END BLOCK 2
END BLOCK 1
leave this program and never come back

I would usually prefer something less magical, though. Why not a structure like

sub cleanup { ... }
END { &cleanup }

if (need_to_exec()) {
    cleanup();        # same thing END was going to do anyway
    exec( ... );
}

?