Odd characters in Telnet prompt

bih71 has asked for the wisdom of the Perl Monks concerning the following question:

I am having problems with NET::TELNET from my pc to a unix platform and from there telnet to a second unix like platform. On the final platform I want to put it into a command mode. However the prompt I get back from the shell is not being recognised due to some odd characters being returned. My code is simply:-

    $telnet->prompt('/> $/');
    $telnet->print('ncli');
[download]

and the output I get is:-

$ ncli
[1m
[ManagedElement=1]> [m
[download]

These last three characters in hex are 1B 5B 6D.

If I do the same operation manually from the same intermediate node (using the unix telnet command) I see:-

$ ncli
[ManagedElement=1]>
[download]

Any ideas on how I can either live with these characters (i.e. make the prompt accept them) or stop them all together.

THanks...bih71

Comment on Odd characters in Telnet prompt Select or Download Code

Replies are listed 'Best First'.
Re: Odd characters in Telnet prompt by MidLifeXis (Monsignor) on Dec 05, 2008 at 16:46 UTC
It seems to me that you may have ANSI escape characters in your prompt. Perhaps this is used for highlighting parts of the prompt on an appropriate device. Either turn off the fancy stuff on the remote side, have the remote side id your script and turn them off for you, or include the fancy characters as an alternation in your prompt string - `\xFF` (see perlre). --MidLifeXis	[reply] [d/l]
Re: Odd characters in Telnet prompt by Perlbotics (Archbishop) on Dec 05, 2008 at 21:13 UTC
As MidLifeXis already explained, it's a problem with ANSI escape sequences. The documentation of Net::Telnet describes the effect in section Connecting to a Remote MS-Windows Machine. If you cannot disable the highlighting at the server side, cleaning up the response is advised. Maybe the following node allows you to save some effort: clean Telnet ANSI escape codes: VT52 and VT100	[reply]