From: Dossy <dossy@...>
Date: 2002-06-16T22:48:15+09:00
Subject: Re: Question: how to  do (repeated) bidirectional communication with another process via stdin/stdout ?

On 2002.06.16, Carsten Gronski <cgronski@web.de> wrote:
> Thanks, but flushing won' t help. Something like this does not work. 
> the program hangs, when trying the second write. 
> .. 
> if (ke != nil)
>     ke.syswrite(loginCall)
>     ke.flush()
>     ke.each("\n") { |line| puts(line) }
>     # we get until here
>     # this does not get through

Right, because the #each will iterate until the remote side closes
their end.  What you need to do is read only as many lines as you
need or expect or read until a certain string is received, or
what have you.

If you're going to use EOF to signal "end of transmission" then
that's what you'll have to use, but then you can't continue to
send and receive like you want.  You need to designate some kind
of EOT (end of transmission) sequence so you can keep the connection
open.

>     ke.syswrite(sysInfoCall)
>     ke.flush()
>     # we never get here -- program hangs !!
>     ke.close_write
>     ke.each("\n") { |line| puts(line) }
>     ke.close
> end

-- Dossy

-- 
Dossy Shiobara                       mail: dossy@panoptic.com 
Panoptic Computer Network             web: http://www.panoptic.com/ 
  "He realized the fastest way to change is to laugh at your own
    folly -- then you can let go and quickly move on." (p. 70)