Returns the directory part of a given file path.
dirname(path)
The directory is the contents of path
before the last path separator
(unless it is significant - e.g. for the root directory - in which case
it is retained). Added in version 7.00.1352510000 20121109.
No filesystem checks are performed, as this is a text/parsing function;
thus ".
" and "..
" are not significant.