extension

Returns the file extension including the leading dot. Returns an empty string if the file has no extension.

Example:

    var path = new Path ("/tmp/file.txt");
    assert (path.extension () == ".txt");
    var noExt = new Path ("/tmp/Makefile");
    assert (noExt.extension () == "");

Returns:

the file extension (e.g. ".txt"), or "" if none.