是否有处理IO的组长协议的规范?

The Erlang Rationale (video) 或 (slides) ;是一个很好的信息源,源代码也是 user.erl .

简而言之:

  {io_request, From, ReplyAs, Request}
  %From is the process to send the reply to, 
  %ReplyAs is any term the caller desires to 
  %match up the request and the response. (returned verbatim in the reply)
  {io_reply, ReplyAs, Reply}

user.erl中的一些请求:

 {put_chars, IoList} % puts the iolist
 {put_chars, M,F,A} % puts the result of apply(M,F,A)
 {get_geometry, 'rows' | 'columns'} % returns the number of rows or columns of the console
 {get_line, Prompt} % calls io_lib:collect_line(Prompt)
 {get_chars, Prompt, Mod, Func, ExtraArgs} 
 {get_until, Prompt, Mod, Func, Args}
 {setopts, Options} % only option supported by user is 'binary' 
                    % (binary mode if present in Options, list mode otherwise)

此处详细描述了Erlang I/O协议:

http://www.erlang.org/doc/apps/stdlib/io_protocol.html