red code

[ignatov]

%% Assumes normalized name
absname_vr([$/ | NameRest], [Drive, $\: | _]) ->
    %% Absolute path on current drive.
    [Drive, $\: | NameRest];
absname_vr([Drive, $\: | NameRest], [Drive, $\: | _] = Cwd) ->
    %% Relative to current directory on current drive.
    Cwd ++ "/" ++ NameRest;
absname_vr([Drive, $\: | NameRest], _) ->
    %% Relative to current directory on another drive.
    case prim_file:get_cwd([Drive, $\:]) of
	{ok, DriveCwd}  ->
	    DriveCwd ++ "/" ++ NameRest;
	{error, _} ->
	    [Drive, $\:, $/] ++ NameRest
    end.

from erlang/lib/erts-12.3.2.13/src/erl_prim_loader.erl