Joining A List Of Binaries In Erlang

The binary module provides an easy way to split binaries using split/2,3, but what if you want to join a list of binaries back together?

-spec binary_join([binary()], binary()) -> binary().
binary_join([], _Sep) ->
  <<>>;
binary_join([Part], _Sep) ->
  Part;
binary_join(List, Sep) ->
  lists:foldr(fun (A, B) ->
    if
      bit_size(B) > 0 -> <<A/binary, Sep/binary, B/binary>>;
      true -> A
    end
  end, <<>>, List).

It works just like you would expect:

binary_join([<<"Hello">>, <<"World">>], <<", ">>) % => <<"Hello, World">>
binary_join([<<"Hello">>], <<"...">>) % => <<"Hello">>

Hope you find this useful!