use telnet to router with expect

fionbarr has asked for the wisdom of the Perl Monks concerning the following question:


use strict;
use warnings;
use Expect;

my $command = Expect->spawn("telnet 000.000.000.000");

print "looking for 'login:'\n";
unless($command->expect(10, "login:")) {
    die "timed out";
    }

print $command "<user>\n";

unless($command->expect(60, -re=> 'assword: ?')) {
    die "timed out";
    }

print $command "<password>\n";


unless($command->expect(60, -re=> 'cr.*')) {
    die "timed out";
    }

print "------------------\n";

print $command "show inventory\n";

$command->hard_close();
[download]

I am using the above to run the command 'show inventory' on a router I am logging into. The command does not run, should it work? Am I going about this wrong?

Comment on use telnet to router with expect Download Code

Replies are listed 'Best First'.
Re: use telnet to router with expect by RMGir (Prior) on Mar 14, 2014 at 13:18 UTC
"Does not run" meaning the spawn fails? Or at a later step? You might want to add an `or die "Expect spawn failed, error $!";` [download] to the end of your spawn command - that might tell you WHY it's failing... I assume 000.000.000.000 isn't the IP address you're actually using - but if it is, that would explain the failure :) Mike	[reply] [d/l]
Re^2: use telnet to router with expect by fionbarr (Friar) on Mar 14, 2014 at 13:52 UTC
thanks Mike...everything works except the 'show inventory' command. The login succeeds and I see the router prompt. At that point, the script says: 'print $command "show inventory"' and the command does not execute.	[reply]
Re^3: use telnet to router with expect by RMGir (Prior) on Mar 14, 2014 at 15:05 UTC
Interesting... I'd download a copy of wireshark (a.k.a. tcpdump) and look at what goes over the wire when you do the command interactively with telnet - perhaps there's a \r sent somewhere you're using a \n, for example. Mike	[reply]
Re^3: use telnet to router with expect by RMGir (Prior) on Mar 14, 2014 at 19:16 UTC
Another possibility - maybe "hard_close" is closing the command before the server can respond? What happens if you switch that to "soft_close", or even expect something you'd see at the end of the inventory before closing? Mike	[reply]