reading and writing rules from and to files

Hi @all,

Exist there an easy possibility in SWI-Prolog to read a file containing 
prolog rules and to write it back to another file, keeping all origin 
variablenames, spaces, cariage returns, comments (% and /*  ...*/ ) ...?
My intention is to read a file, change the rules in the file a little bit 
and then write these rules back to another file.
Thank you very much and Merry Christmas
Marbod