Returns a name comprised of all of the path components in name excluding the last element. If name is a relative file name and only contains one path element, then returns "." (or ":" on the Macintosh). If name refers to a root directory, then the root directory is returned. For example,
file dirname c:/
returns c:/.
Note that tilde substitution will only be performed if it is necessary to complete the command. For example,
file dirname ~/src/foo.c
returns ~/src, whereas
file dirname ~
returns /home (or something similar).