ROOT_NAME get root name
ROOT_NAME(P) returns the root name of P. root_name is the drive letter on Windows without the trailing slash or an empty string if P is not an absolute path. on non-Windows platforms, root_name is always an empty string.
ROOT_NAME(P) returns the root name of P. root_name is the drive letter on Windows without the trailing slash or an empty string if P is not an absolute path. on non-Windows platforms, root_name is always an empty string.