basename removes all of the path up to and including the last
path separator (if any). dirname returns the part of the path up to but
excluding the last path separator, or "." if there is no path
character vector, containing path names.
A character vector of the same length as path. A zero-length
input will give a zero-length output with no error. Paths not containing any separators are taken to be in the current
directory, so dirname returns ".". If an element of path is NA, so is the result. "" is not a valid pathname, but is returned unchanged.
Behaviour on Windows
On Windows this will accept either \ or / as the path
separator, but dirname will return a path using /
(except if on a network share, when the leading \\ will be
preserved). Expect these only to be able to handle complete
paths, and not for example just a network share or a drive. UTF-8-encoded path names not valid in the current locale can be used.
For dirnametilde expansion of the path is done. Trailing path separators are removed before dissecting the path,
and for dirname any trailing file separators are removed
from the result.