OK, I think I finally understand your earlier comment about
directory/filename distinction. I've quickly scanned the hyperspec on
this and can't find the relevant section, so am referring this to our
resident expert Paul Dietz/
...
Looking at this has made me notice a bug -- one can apparently open
streams with directory pathnames, but reading of course fails. I am
committing changes** designed to fix this simply for now, by ensuring
that open_stream and probe-file (and file-write-length, file-author
...) fail (i.e. return nil) on directories. Eventually we might want
to allow open to succeed, returning a 'user-defined' stream, and have
read thereon return stat structures for the files therein. The only
standardized interface to directories under lisp I can find is
(directory ...), not surprisingly, so with this set of changes, this
will be the only thing you can do with a pathname that refers to a
directory, trailing slash or not.