Hi,

How does one save and read third-party data in tuc file at the lua end?

I am trying to write a module t-ifchanged that defines a \doiffilechanged 
macro that provides the functionality of mtxrun --ifchanged without 
calling an external program (This is meant to be a support module for 
t-vim, where the external calls to mtxrun are too time consuming).

I can successfully write additional data to the tuc file, but cannot 
figure out how to initialize the data from tuc file. (See attached file). 
Any hints are welcome.


Aditya