Re: [Expectperl-discuss] Can I use expectperl from a sub-process?

[Ed R. <er...@pa...>]

Austin Schutz writes:
> On Sat, Mar 02, 2002 at 12:40:25AM -0500, Ed Ravin wrote:
> > Here's what I'd like to do with Expect.pm:
> > * Spawn a telnet to somewhere.
> > * Invoke a subshell
> > *   From within that subshell, call another Perl program one or more
> > times to interact with the telnet process spawned by the parent process.

> 	Thirdly, you could have the called perl program call the telnet
> expect process and work with it as if it were any other process.  It's hard to
> tell (for me anyway) what you're trying to accomplish.

What I want to do (and why this option won't work) is to set up Kerberized
telnet or ssh session to a Cisco router, drop into a shell, and be able
to run shell commands that manipulate the router via the session.  I've
already got this working with regular (cleartext) telnet sessions - the
filehandle with the telnet session is inherited by telnet's children  - I
subshell from telnet and then have the Perl/Expect program use exp_init()
to hook up to fd3 and I'm all set.  I can call the Perl/Expect program
multiple times to manipulate the router via the Telnet session, I can call
the editor or other shell programs as needed, and when I'm done I exit
the shell and return back to the telnet prompt.

But for an ssh or Kerberized telnet session, that won't work - telnet or
ssh has to stay running to encrypt/decrypt the data - the only way to
talk to the remote router is via the pty of ssh/telnet.  I could have
the perl/expect program start ssh/telnet, but my program is meant to be
a tool that you run multiple times against the router, so I want the ssh/
telnet to persist.

> 	Another way is to have an expect script that does interact() at
> some point and uses named pipes as i/o. I think that's how things like
> kibitz work. Performance-wise it's less efficient, but probably easier to
> code.

Easy to code, I like that :-).  I had earlier tried using ksh93,
which has a built-in for doing this - when you
start a process and background it with "|&" instead of "&", you
end up with two pipes (meant for use with ksh's "read -p" and "print -p"
commands).  I suppose I can try hooking one of the pipes to the Expect
object, and teaching my script to send the output data for the telnet/ssh
session to the other?