Elixir port using named pipe via UNDOCUMENTED open_port/2 functionality

from_pipe.ex

defmodule FromPipe do
  #
  # NOTE: this use of ports is based on UNDOCUMENTED functionality
  # of the open_port/2 function - i.e. could stop working
  # in any future release
  # http://erlang.org/doc/man/erlang.html#open_port-2
  #
  # See also:
  # Erlang and Named Pipes
  # https://gist.github.com/jaredmorrow/1c342c6e9156eddd20b2
  #
  # Reading Named Pipes with Elixir
  # https://blog.ironbay.co/reading-named-pipes-with-elixir-c5c614a32f25
  #
  # Rate limiting Ports
  # https://elixirforum.com/t/rate-limiting-ports/9094
  #
  # Elixir port using named pipe with forwarding script
  # https://gist.github.com/peerreynders/cbefdef71ce85fa0017d8d3262a9e1cd
  #
  # Elixir port using named pipe with releasing script
  # https://gist.github.com/peerreynders/fb92fa4fe78d825ff82803f78f2fd551
  #
  @pipe_name "/tmp/testpipe"
  @from_pipe_prep "./from_pipe_prep"

  # delete previous named pipe and create a fresh, empty one
  defp prep() do
    path = Path.expand(@from_pipe_prep)
    System.cmd(path, [@pipe_name])
  end

  defp start do
    # IMPORTANT: pipe_name needs to be a charlist
    @pipe_name
    # to use "UNDOCUMENTED" Erlang functionality
    |> to_charlist()
    |> Port.open([:binary, {:line, 1024}, :eof])
  end

  defp stop(port) do
    Port.close(port)
    :ok
  end

  defp loop(port) do
    receive do
      {^port, {:data, {:eol, "quit"}}} ->
        stop(port)

      {^port, {:data, {:eol, data}}} ->
        IO.puts("eol data: #{data}")
        loop(port)

      {^port, {:data, {:noeol, data}}} ->
        IO.puts("noeol data: #{data}")
        loop(port)

      msg ->
        IO.puts("other: #{inspect(msg)}")
        loop(port)
    end
  end

  def run() do
    prep()
    loop(start())
  end
end

from_pipe_prep

#!/bin/bash
# file: from_pipe_prep pipe_name
if [[ -p $1 ]]; then
  rm -f $1
fi

mkfifo $1

session.md

1$ iex
Erlang/OTP 21 [erts-10.1.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe] [dtrace]

Interactive Elixir (1.7.4) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> c("from_pipe.ex")
[FromPipe]
iex(2)> FromPipe.run()   
eol data: hello
eol data: world
noeol data: 1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEF
eol data: GHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ
:ok
iex(3)> 

2$ echo hello >/tmp/testpipe
2$ echo world >/tmp/testpipe
2$ echo 1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ >/tmp/testpipe
2$ echo quit >/tmp/testpipe
2$