parse-colon-path

parse-colon-path is a compiled Lisp function in `files.el'.

(parse-colon-path SEARCH-PATH)

Explode a search path into a list of directory names.
Directories are separated by `path-separator' (which is colon in
GNU and Unix systems). Substitute environment variables into the
resulting list of directory names. For an empty path element (i.e.,
a leading or trailing separator, or two adjacent separators), return
nil (meaning `default-directory') as the associated list element.