anchor.diff:                  Host, "/", Method, Path],
       lists:flatten(ProxyUrl).
   
  --spec safe_rename(string(), string()) -> 'ok' | {'error', 'file_exists'
  -    | {'chmod_failed', _} | {'rename_failed', _}}.
  +-type rename_errors() :: file_exists| {chmod_failed, _} | {rename_failed, _}.
  +-spec safe_rename(string(), string()) -> ok | {error, rename_errors()}.
   safe_rename(Src, Dst) ->
       case prim_file:read_file_info(Dst) of
           {error, enoent} ->
  
positive.code:             Error
      end.
  
  -spec diskspace(nonempty_string()) ->
      {'error', 'invalid_output' | 'invalid_path'} | {'ok', diskinfo()}.
  diskspace(Path) ->
      case lists:reverse(string:tokens(os:cmd(["df -k ", Path]), "\n\t ")) of
          [_, _, Free, Used|_] ->
  
negative.code:         _ -> {error, file_exists}
      end.
  
  -spec concatenate(file:filename(), file:filename()) -> ok | {error, term()}.
  concatenate(Src, Dst) ->
      {ok, SrcIO} = prim_file:open(Src, [read, raw, binary]),
      {ok, DstIO} = prim_file:open(Dst, [append, raw]),
  