TCL Expect Buffer and SSH Problem?

[tktuffkid]

I am experiencing some unexpected symptoms between Expect and SSH and was wondering if anyone could provide some insight. In a nutshell, I want to create a proc that flushes out the Expect buffer of residual characters from an SSH session. I thought of doing this by merely "expecting" a catch all regexp. However, this doesn't seem to work.

To simplify, I have provided an example below.

Given:
Prompt Format = [JohnDoe@1.2.3.4 /home]$

1) Spawn an SSH Session to server 1.2.3.4 as user JohnDoe

spawn ssh -l JohnDoe -X 1.2.3.4

2) Expect a Password prompt

expect -re {[Pp]assword:}

3) Send in JohnDoe's password

send "abc123\r"

4) Expect the User's Bash Prompt based on the given prompt format defined above. In this case, I use a regexp of a right square bracket followed by a literal dollar-sign (not an anchor)

expect -re {]\$}

5) Execute any Linux command

send "ls -al\r"

6) Execute the following two Expect commands

6a) expect -re {.*}
6b) expect -re {]\$}

My problem is that I would expect the regexp {.*} to catch everything that the spawned SSH session is returning. However, it is not. In other words, step #6a doesn't catch anything other than a single blank space (based on exp_internal debug). It's as though the SSH session does NOT want to let go and echo anything from step #5...no matter how long I wait. However, if I execute step #6b, I then see all of the output.

Can anyone tell me why the Expect command in step #6a is not catching everything? Any help would be much appreciated and thank you in advance.

 

[macd68]

Try a newline...and make sure that the command is received.

 

[tktuffkid]

That didn't work either. With "exp_internal 1" configured, it does show the command being sent to the spawn_id.

 

[macd68]

Example code. This code is untested but the approach should work fine for you.

#!/usr/bin/tclsh
package require Expect

set timeout 20
set prompt1 ".*asswor.*"
set prompt2 ".*>."
#customize the above to your system

array set optarray {}

proc getopt {str lst} {
global optarray
set cnt 0

            foreach x [split $str ""] {
                      set opt "-$x"
                      if {[set ind [lsearch -exact $lst $opt]] >= 0} {
                          set optarray($opt) [lindex $lst [expr $ind + 1]]
                          incr cnt
                      }
            }
return $cnt
}

puts -nonewline "\nUsage: -d = debug, -h = host, -u = username.\n"
getopt "dhu" $argv
if {[info exists optarray(-d)]} {exp_internal 1; log_user 1}
parray optarray

if {[catch {spawn ssh $optarray(-u)@$optarray(-h)} err]} {
    send_user "Error occurred during spawn = $err\n"
    exit 1
}

expect {

       -re $prompt1 {
                    send_user "\nPassword prompt for user $optarray(-u) on host $optarray(-h): "
                    stty -echo
                    set pw [get_user]
                    stty echo
                    send "$pw\r\n"
                    exp_continue
        }

        -re $prompt2  {
                    #login successful
                    send "ls -al\r\n"
                    expect -re "(.*)\n$prompt1" {
                           send_user "Command returned information: $expect_out(1,string), $expect_out(buffer)\n"
                           close $spawn_id
                           wait
                           exit 0
                    }
        }
                                        
         timeout {send_user "$spawn_id failed to connect within $timeout seconds\n"}
         eof {send_user "Remote host closed connection.\n"}
}.