From: Doug Phillips <DPhillips@...>
Date: 2007-05-19T11:11:36+09:00
Subject: Re: ssh / popen / stdin weirdness

> -----Original Message-----
> From: Mike Cahill [mailto:mike.cahill@comcast.net] 
> Sent: Friday, May 18, 2007 8:56 PM
> To: ruby-talk ML
> Subject: ssh / popen / stdin weirdness
> 
> Sorry I can't figure out how to find the cause of this 
> myself.  I'm sure there's some article somewhere I'm not finding.
> 
> on RHEL4 u3, ruby 1.8, create:
> 
> ===
> app.rb: 
> 
>   my_pipe = IO.popen("ssh foreign-host 'cat filename')
>   file_contents = my_pipe.read
>   my_pipe.close
> 
>   inp = $stdin.read
>   puts "returning " + inp
> 
> ====
> 
> Run this app from this host (call it ServerB):
> ruby app.rb <<EOF
> hi there
> EOF
> 
> You get "returning hi there", as expected.
> 
> ----
> Now, from ServerA (public keys have been pushed), run:
> 
> ssh ServerB 'ruby app.rb' <<EOF
> hi there
> EOF
> 
> it fails, in that inp receives nothing from $stdin.
>  ----
> 
> now, go back to app.rb, remove the first three lines so 
> there's no call to IO.pipe.
> 
> run it again, it works.
> 
> why does $stdin get "moved" when the app is called remotely 
> and opens a pipe?

SSH doesn't fork a TTY when a command is given.  Try calling ssh with
the -t flag.
-Doug