Re: [Expectperl-discuss] Nested telnet sessions using Expect.pm module

[Hailey N. <Hai...@Su...>]

Hi D. Basham,

It's definitely very helpful. Chris Muth has sent me an example and I got
my stuff to work with that. But your info is also a great help to me.

Thanks,
HAiley
>
>
>>>> Note:  A know B but doesn't know C - in another words, to get to C you
> have
>>>> to go through B.
>
> Yes.. well, I guess it depends on what you're trying to say behind the
> words.   Remember that you're spawning ONE process (or should be).  Once
> you've done that and successfully logged into A, you should INVOKE telnet
> client on A to get to B, so there's no more "spawning" (from a perl module
> perspective), as B and C have no clue what the heck SPAWN is.. they just
> know what telnet is.  Just imagine that you are invoking telnet on the
> command line from host to host to host, and that's ultimately what expects
> doing with the single telnet session you spawned to A.  Imagine it that
> way and you should be able to see enough of what's going on to know how
> to use expect and code it.  Remember that each time you hop, the STDOUT
> and STDERR channels get lashed together, and become STDIN to the thing
> that created it (parent.)  They all get lashed together like the Alaskan
> pipeline, all the way back to your original spawned process in your
> expect script.  In this daisy-chain telnet example you're trying to do,
> it is the only STDIN that your script should be dealing with.
>
> I don't know if that's the understanding you need, or if I'm confusing you
> more.  Bottom line, If you can do it from the command line, i.e., telnet
> from A to B to C and so forth, then so can expect.  If you can't do it,
> then neither can expect.  It's that simple.  All expect does is provide a
> way to automate the steps.  The only difference between opening a process
> in Perl vs. Expect is that perl (by itself) cannot open a bi-directional
> pipe to a process.  I.e., it can do this
>
>      open (TELNET, " telnet $HOSTA | ");
>
> which would allow you to read from the session, or you can do this:
>
>      open (TELNET, "| telnet $HOSTA ");
>
> to write to the process, but you cannot do both at the same time like
> this:
>
>      open (TELNET, "| telnet $HOSTB | ");
>
> that's where Expect can help.  The telnet module is an alternative that
> also does this, but only for telnet.  Can't spawn a chess program on the
> command line and interact with it using telnet module, but you can do it
> using Expect (for all you telnet.pm zealots out there, that's the
> difference)
>
> If you want to look at primitive code that represents this idea, then it
> would look something like this:
>
> use Expect;
>
> $HOSTA=xx.xx.xx.1;
> $HOSTB=xx.xx.xx.2;
> $HOSTC=xx.xx.xx.3;
>
> $username="abc";
> $password="123";
>
># ------------
># telnet to A
># ------------
> my $exp = Expect->spawn("telnet $HOSTA") or die "Cannot spawn telnet: $!
> \n";
> $timeout=20;
> expect($timeout, "login: ");
> $exp->send("$username\n");
> expect($timeout, "password: ");
> $exp->send("$password\n");
> $expect($timeout, '-re', "[%#>] $");         # $HOSTA prompt
>
># ------------
># telnet to B
># ------------
> $exp->send("telnet $HOSTB\n");
> expect($timeout, "login: ");
> $exp->send("$username\n");
> expect($timeout, "password: ");
> $exp->send("$password\n");
> $expect($timeout, '-re', "[%#>] $");         # $HOSTB prompt
>
># ------------
># telnet to C
># ------------
> $exp->send("telnet $HOSTC\n");
> expect($timeout, "login: ");
> $exp->send("$username\n");
> expect($timeout, "password: ");
> $exp->send("$password\n");
> $expect($timeout, '-re', "[%#>] $");         # $HOSTC prompt
>
>
> Braindead simple example, but you should get the idea.  Do a perldoc on
> Expect.pm and print it out, go to staples and buy a binder, put it in
> there and carry it around / put it on your desk at work also.  If you
> REALLY want to get nuts and rule the world with Expect, go out and buy
> Don Libes most excellent O'Reilly book.  Tcl is such a simple language,
> that you would have no problem figuring enough of it out on the fly to
> literally use this book as a supercharged reference for the Perl module,
> that is, unless you're a Perl zealot and can't for religious reasons..
> although the perl module is not 100% translation, it's close enough for
> government work (so the saying goes.)
>
>
> Anyways, hope this helps you man.
>
>
>
>
>
>
>                      Hailey Nguyen
>                      <Hai...@Su...>                     To:
> Chris Muth <mut...@mc...>                                     Sent
> by:                                    cc:     Hailey Nguyen
> <Hai...@Su...>,
> exp...@li...urc
> exp...@li...
> eforge.net                                  Subject:     Re:
> [Expectperl-discuss] Nested telnet
> sessions using   Expect.pm module
>                      10/02/2003 04:11 PM
>
>
>
>
>
>
>
> Hi Chris,
>
>>>> First you will have to login to A.  That involves what you have, plus
>>>> you will have to $exp->expect() for whatever telnet responds with when
>>>> it asks for the password.  Then use a $exp->send() to send the
> password.
>>>> Then $exp->expect() for the prompt on A.  Once you are logged into A,
>>>> use a $exp->send() to call telnet $B on A to login to B, $exp->expect()
>>>> for the password prompt, and then $exp->send() it.  Once logged into B,
>>>> do the same to login to C, and the same for D, and the same for ...
>
> Still struggling with this. As soon as I logged into B from A I lose
> control of that session/connection. So $exp->send() won't do anything.
> Did you write something like this before. Can I have an example?
>
> Note:  A know B but doesn't know C - in another words, to get to C you
> have to go through B.
>
> Thanks a million,
> Hailey
>
>
>>>>>
>>>>> Please show me how to do nested telnet sessions using Expect.pm
> module?
>>>>>
>>>>> 1- telnet to machine A
>>>>> 2- from A to mcahine B
>>>>> 3- from B to machine C
>>>>>
>>>>> -----
>>>>> use Expect;
>>>>>
>>>>> my $exp = Expect->spawn("telnet $somehost")
>>>>>    or die "Cannot spawn telnet: $!\n";
>>>>>
>>>>> ...
>>>>>
>>>>> -----
>>>>> Your help is greatly appreciated. Please reply directly to me since
>>>>> I am not on the alias.
>>>>>
>
>
>
>
>
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