copy

#!/usr/bin/env escript

%% copy -- copy input to output
%%
%% We're not defining primitives like in the book,
%% We can't detect ENDFILE with io:get_line/1, and
%% it already receive only one line so no need to
%% detect ASCII NEWLINE as well.
%%
%% Since we can't detect ENDFILE, we can mimic ed(1)
%% behavior so that a "." in an empty line will quit.
%%
%% Correction: we can't detect ENDFILE in Erlang Shell,
%% but when running from terminal as an escript program,
%% you can pattern match Ctrl-D as eof.
copy() ->
    Input = ststd:getc(),
    copy(Input).

copy(eof) ->
    {ok, eof};
copy(".\n") ->
    {ok, eof};
copy(Input) ->
    ststd:putc(Input),
    copy().

main(_) ->
    copy().