Is there a reference parasitic extraction script for Magic VLSI that is up to date?

Parasitic capacitance extraction, or a full R-C extraction?

Full RC

I have it written down somewhere. It's a bit complicated because to ensure that the full R-C result is meaningful, you need to flatten the circuit. It would go something like this:

load <cellname>
flatten my_flat_cell
load my_flat_cell
extract do local
extract all
ext2sim labels on
ext2sim
extresist tolerance 10
extresist
ext2spice lvs
ext2spice cthresh 0
ext2spice extresist on
ext2spice

This would result in an output file

my_flat_cell.spice

that would be the full R-C extracted circuit.