cf.erl

-module(cf).

-export([compare_files/2]).

compare_files(FileName1, FileName2) ->
    OS1 = ordset_from_file(FileName1),
    OS2 = ordset_from_file(FileName2),
    OS1_uniq = ordsets:subtract(OS1, OS2),
    OS2_uniq = ordsets:subtract(OS2, OS1),
    case {OS1_uniq, OS2_uniq} of
        {[],[]} -> io:format("files ~s and ~s are identical~n", [FileName1, FileName2]);
        {_, []} -> print_uniq(FileName1, OS1_uniq);
        {[], _} -> print_uniq(FileName2, OS2_uniq);
        {_,  _} ->
            print_uniq(FileName1, OS1_uniq),
            print_uniq(FileName2, OS2_uniq)
    end,
    ok.

ordset_from_file(FileName) ->
    {ok, F} =  file:open(FileName,[read]),
    OS = ordsets:from_list(read(F)),
    file:close(F),
    OS.

read(F) ->
    read(F, []).

read(F, Acc) ->
    case file:read_line(F) of
        eof ->
            Acc;
        {ok, Data} -> 
            {I,_} = string:to_integer(lists:nth(3, string:tokens(Data, ";"))), % выбираем третью колонку
            read(F, [ I | Acc ])
    end.

print_uniq(FileName, List) ->
    io:format("file ~s contains uniq: ", [FileName]),
    [ io:format("~w ", [X]) || X <- List ],
    io:format("~n").