filelib:fold_files(Directory, ".*", true, fun (FileOrDirPath, Acc) -> Worker(FileOrDirPath), Acc end, []).

-module(procdir).
-export([start/0]).

start() ->

Directory = "c:/",
Worker = fun (File) -> io:format("~s~n", [File]) end,

filelib:fold_files(Directory, ".*", true, fun (FileOrDirPath, Acc) -> Worker(FileOrDirPath), Acc end, []).

process_dir(Directory, Worker).

-module(procdir).
-export([start/0]).

start() ->

Directory = "c:/",
Worker = fun (File) -> io:format("~s~n", [File]) end,

process_dir(Directory, Worker).

list_dir_path(Directory) ->
{ok, Files} = file:list_dir(Directory), lists:map(fun (File) -> filename:absname(File, Directory) end, Files).

process_dir(FileOrDirPath, Worker) ->
lists:foreach(fun (FODP) -> Worker(FODP), case filelib:is_dir(FODP) of true -> process_dir(FODP, Worker) ; _ -> false end end, list_dir_path(FileOrDirPath)).