LinuxQuestions.org - expect script to telnet into a router

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expect script to telnet into a router

I have a Thomson TG784 router, where I would like to log in automatically and execute dhcp server lease flush command.

When I log in using telnet, the process is following:

Code:

martin@martin-desktop:~$ telnet 192.168.1.254

Trying 192.168.1.254...

Connected to 192.168.1.254.

Escape character is '^]'.

Username : Administrator

Password : **********

------------------------------------------------------------------------



                            ______  Thomson TG784

                        ___/_____/\ 

                        /        /\\  8.2.3.A

                  _____/__      /  \\ 

                _/      /\_____/___ \  Copyright (c) 1999-2009, THOMSON

              //      /  \      /\ \

      _______//_______/    \    / _\/______ 

      /      / \      \    /    / /        /\

  __/      /  \      \  /    / /        / _\__ 

  / /      /    \_______\/    / /        / /  /\

 /_/______/___________________/ /________/ /___/  \ 

 \ \      \    ___________    \ \        \ \  \  /

  \_\      \  /          /\    \ \        \ \___\/

    \      \/          /  \    \ \        \  /

      \_____/          /    \    \ \________\/

          /__________/      \    \  /

          \  _____  \      /_____\/

            \ /    /\  \    /___\/

            /____/  \  \  /

            \    \  /___\/

              \____\/



------------------------------------------------------------------------

_{Administrator}=>exit

Connection closed by foreign host.

martin@martin-desktop:~$

So I did following expect script:

Code:

root@martin-desktop:/home/martin# cat expect_script.sh 

#!/usr/bin/expect -f

set timeout 20

set echo  off



#router username

set name Administrator

#command to execute

set routercmd "dhcp server lease flush\r"

#router password

set pass 1234567890

#router IP address

set routerip 192.168.1.254



spawn telnet $routerip

# send username & password

expect "Username : "

send "$name\r"

expect "Password : "

send "$pass\r"

expect -i "_{Administrator}=>"

send $routercmd



exit

root@martin-desktop:/home/martin#

And now when I execute expect_script.sh, it fills in the username, but stops in password prompt:

Code:

root@martin-desktop:/home/martin# ./expect_script.sh 

spawn telnet 192.168.1.254

Trying 192.168.1.254...

Connected to 192.168.1.254.

Escape character is '^]'.

Username : Administrator

Password :

However, the password really is 1234567890. Any ideas, what might be wrong here? :rolleyes:

Have you considered using `autoexpect` to try the session, and have the script generated automatically?

Example:

Code:

$ autoexpect telnet 192.168.1.254

and go from there.

If interested, check the man page for autoexpect.

(P.S. - maybe you're pretty good with expect :) but I'm not - I found autoexpect to be really handy.)

Good luck!

GrapefruiTgirl, thanks! This autoexpect is very handy indeed. The problem with my expect_script.sh was, that I didn't wait for asterisk characters from 192.168.1.254 :)

However, I would like to make an expect script, which asks for username and password when script is executed. Password query from user should be in following manner:

Code:

stty_orig=`stty -g`

stty -echo

read secret

stty $stty_orig

So far I have come up with this, but it's not quite what I want:

Code:

#!/usr/local/bin/expect -f

set password [lrange $argv 0 0]



set timeout -1

spawn telnet -K 192.168.1.2

match_max 100000

expect -exact "Username: "

send -- "martin\r"

expect -exact "Password: "

send -- "$password\r"

expect -exact "homeswitch#"

send -- "exit\r"

expect eof

Is it possible at all to avoid plain text passwords in expect script files? :rolleyes:

The "plain passwords in scripts" is a somewhat common query for which I don't have a known-good suggestion. Try an LQ search for "plain text password script" and look at the first half-dozen results or so, and see if anything looks appealing.

I like what it appears you are doing above there in post #3 -- but that still requires human interaction, yes? Of course, if I'm understanding this whole situation correctly, you (a human) are actually executing this script somehow manually anyway, aren't you? If so, what would be wrong with having to input the password upon script execution, rather than store it inside the script? (I'm thinking of Bash's `read` command in silent mode -- does expect have such a thing?)

Quote:

Originally Posted by GrapefruiTgirl (Post 4052616)

GrapefruiTgirl, basically you summarized my question very well- is there a similar thing in expect as there is 'read' in bash?

Martin,

from the `expect` man page:

Code:

expect_user [expect_args]



    is  like  expect  but  it  reads characters from stdin (i.e. keystrokes from the user).

    By default, reading is performed in cooked mode. Thus, lines must end with a return in order

    for expect to see them.  This may be changed via stty (see the stty command below).

And further down, there's the interact option.. Perhaps one of these will do the trick.