When
           using Unix or MSDOS syntax, the return value conforms to the behav-
           ior of the Unix shell command dirname(1).  This is usually the same
           as the behavior of fileparse(), but differs in some cases.  For
           example, for the input file specification lib/, fileparse() consid-
           ers the directory name to be lib/, while dirname() considers the
           directory name to be .).

##</code><code>##

$ dirname foo/bar
foo
$ dirname foo/bar/
foo
$ dirname foo/bar/.
foo/bar