The "File Utilities Package" is a set of routines for direct file management and access from inside the MOO, developed and written by Jaime Prilusky and Gustavo Glusman, Weizmann Institute of Science, Israel.
FUP is available on many MOOs, however most will use
a $file_handler interface. Important: at TECFAMOO and
other MOOs you need special permission to use the FUP utilities.
If you are not interested in implementation details and (mostly) locked
built-in functions, go directly to section 15.2
on 
that explains the programmers interface
at TECFAMOO.