How to traverse a directory in eiffel?

Simple

How can I get a list of the files that are inside directory using eiffel?

with recent version of Eiffel, I would recommend to use DIRECTORY.entries

local
    p: PATH 
do
    across dir.entries as ic loop
        p := ic.item.path
            -- then use interface of PATH, such as PATH.name 
    end
end

note that the base_extension library also provides DIRECTORY_VISITOR , which is helpful to iterate recursively on directories