An Erlang module for counting a word occurrence inside a given directory files.

utility.erl

%% part 1: utility module
%% ======================
-module(utility).
-export([count/2]).

%% part 2: count function
%% ======================
count(Dir, Word) ->
   Accumulator = 0,
   CounterPid = spawn(fun() -> counter(Accumulator) end),
   register(counter, CounterPid),
   count_on_dir(Dir, Word).

%% part 3: counter function
%% ========================
counter(Accumulator) ->
   receive 
      stat -> io:format("~p~n", [Accumulator]), counter(Accumulator);
      exit -> io:format("~p~n", [Accumulator]);
      Count -> counter(Accumulator + Count)
   end.

%% part 4: count_on_dir function
%% =============================
count_on_dir(Dir, Word) ->
   Files = list_files(Dir),
   count_on_files(Files, Word).

%% part 5: count_on_files function
%% ===============================
count_on_files([File|RestFiles], Word) ->
   spawn(fun() -> do_count(File, Word) end),
   count_on_files(RestFiles, Word);
count_on_files([], _Word) -> ok.

%% part 6: do_count function
%% =========================
do_count(File, Word) ->
   {ok, OpenFile} = file:open(File, read),
   read_file(OpenFile, Word).

%% part 7: read_file function
%% ==========================
read_file(OpenFile, Word) ->
   case io:get_line(OpenFile, "") of
      eof -> file:close(OpenFile);
      Line -> 
         read_line(Line, Word), 
         read_file(OpenFile, Word)
   end.

%% part 8: read_line function
%% ==========================
read_line(Line, Word) ->
   case re:run(Line, Word, [global]) of
      {match, MatchedList} -> counter ! length(MatchedList);
      _ -> ok
   end.

%% part 9: list_files function
%% ===========================
list_files(Dir) ->
   {ok, Files} = file:list_dir(Dir),
   FilterMap = fun(FileName) ->
      FilePath = Dir ++ "/" ++ FileName,
      case filelib:is_dir(FilePath) of
         true -> false;
         false -> {true, FilePath}
      end
   end,
   lists:filtermap(FilterMap, Files).

utility.sh

$ erl
Eshell V5.10.4  (abort with ^G)
1> c(utility).
2> utility:count("/your/dir", "salam_donya").
3> counter ! stat.
4> counter ! exit.