Can expect return control of a spawned process to a shell script?

duffrecords · 11-19-2009, 08:22 PM

Is it possible to have an Expect script spawn an SSH session, log in, then go into interactive mode and give control of the SSH session to a Bash script? Here's a simplified example of the script so far:

Code:

#!/bin/bash

expect -c "
spawn -noecho ssh $user@$host
expect { 
  "*password:*" { send $password\r\n; interact } 
  eof { exit }
}
exit
"
ls -l | zenity --list --title "Select files" --column "Files" --separator=" " --multiple

As you might guess, I'm trying to create an interactive GUI for several routine SSH commands. Basically, I need to figure out how to pass commands from a local Bash script to a remote machine and make decisions based on feedback from the remote machine. Would it be easier to do this with port forwarding, and if so, can Expect be used to supply the password? RSA is not an option on these servers, unfortunately.

Bhagyesh · 11-19-2009, 08:27 PM

Lets see if this help you understand it much better..

this scripts will "ssh" into the remote machine and will "execute the command" that you pass to be executed on the remote system.

- it will fetch the output to your local screen

Code:

#!/usr/bin/expect -f
# USAGE:
#----------------------------------------------------
# ./ssh-expect.exp 'command to be executed on remote machine'
#----------------------------------------------------

set password [lrange $argv 0 0]
set remote_ipaddr [lrange $argv 1 1]
set scriptname [lrange $argv 2 2]
set arg1 [lrange $argv 3 3]
set timeout -1

spawn ssh root@$remote_ipaddr $scriptname $arg1
match_max 100000

# Look for passwod prompt
expect "*?assword:*"

# Send password to the remote machine
send -- "$password\r"
send -- "\r"

#terminate the connection
expect eof

duffrecords · 11-20-2009, 01:35 PM

Thanks. This is exactly the sort of thing I'm looking for. Does $scriptname represent the command to be executed remotely, or is that $arg1? I'm a little confused by that part. It looks like the file represented by $scriptname would need to exist on the remote server, correct?

duffrecords · 11-22-2009, 12:01 PM

I've managed to get this Expect script to run a remote Bash script specified by $scriptname and have the output of that script appear in my local stdout. That's what I need. However, I also need to forward my local stdin to the remote Bash script. So far the prompt doesn't seem to take any input; it just waits until I press Ctrl-C. How do I do this?

Bhagyesh · 04-28-2010, 02:33 PM

it should be something like this :

./ssh-expect.exp <remote-root-password> <remote-server-ip> <command to be executed>

you can modify the script according to your requirement
set password [lrange $argv 0 0]
set remote_ipaddr [lrange $argv 1 1]
set scriptname [lrange $argv 2 2]
#set arg1 [lrange $argv 3 3]

changing the order of the above variables

FYI..
#set arg1 [lrange $argv 3 3] // sorry about this extra argument // you can remove this and still the script will work fine.

no extra key press the output to be right on your screen

#!/usr/bin/expect -f
# USAGE:
#----------------------------------------------------
# ./ssh-expect.exp '<remote-root-password> <remote-server-ip> <command to be executed>'
#----------------------------------------------------

set password [lrange $argv 0 0]
set remote_ipaddr [lrange $argv 1 1]
set scriptname [lrange $argv 2 2]
set timeout -1

spawn ssh root@$remote_ipaddr $scriptname
match_max 100000

# Look for passwod prompt
expect "*?assword:*"

# Send password to the remote machine
send -- "$password\r"
send -- "\r"

#terminate the connection
expect eof