using expect to log into devices

Sat Jul 21 03:53:04 UTC 2018

I have looked extensively on the web for an answer
and cannot find one, so I come to you guys.  I am
not allowed to use modules in PERL or Python or I 
wouldn't have to do it this way.  I have to do this
all in Expect and I am a newbie at it.

Also, maybe I'm having the Friday afternoon "I want 
to go home" mental block and the answer is right in 
front of my nose.

I have a file with 1000s of devices and another file 
with a list of commands.  The program issues all 
commands for a device and then moves on to the next 
one using nested loops.  In the debug I see the 
"spawn_id expNN" (where NN is a number that, I 
believe is representative of the number of file 
descriptors used in the system) increment only when 
a device does not respond.  As long as a device 
responds before the timeout period I see the expNN 
number does not increase.  As soon as a device 
doesn't respond the expNN count goes up and I can't 
figure out why.  Once I hit a certain expNN the 
program exits ungracefully; usually somewhere between 
2500 and 3500 devices because our FD is set to 256
and that's how long it takes for 256 devices to not 
respond before the timeout period.  Can anyone tell 
me why?  Here is the relevant config snippet.  I've 
tried every iteration of close and wait I found and 
no love...

You'll want to put this into a fixed width font like
Courier New or it'll just be a mess.

foreach element $device {

send_user "\n\n"

send_user "#####################################\n"
send_user "######  BEGIN $element  #######\n"
send_user "#####################################\n"

   spawn ssh -q -o StrictHostKeyChecking=no $username@$element

expect {
  timeout { send_user "\nfailed to get password prompt\n\n"
            send_user "#####################################\n"
            send_user "#######  END $element  ########\n"
            send_user "#####################################\n"
            send_user "\n\n\n"; continue
            close $spawn_id
            wait
          }
  eof { send_user "\nssh failure for $element\n\n"
        send_user "#####################################\n"
        send_user "#######  END $element  ########\n"
        send_user "#####################################\n"
        send_user "\n\n\n"; continue
        close $spawn_id
        wait
      }
  "assword" {
  send "$password\n"
            }
       }

expect {
  timeout { send_user "\npassword did not work or enable mode not 
                        achieved\n\n"
            send_user "#####################################\n"
            send_user "#######  END $element  ########\n"
            send_user "#####################################\n"
            send_user "\n\n\n"; continue
            close $spawn_id
            wait
          }
  eof { send_user "\npassword failure for $element\n\n"
        send_user "#####################################\n"
        send_user "########  END $element  #########\n"
        send_user "#####################################\n"
        send_user "\n\n\n"; continue
        close $spawn_id
        wait
      }
        "" {
              send "term len 0\n"
#             send "skip-page-display\n"

              foreach command $commands {
                expect "#"
                send "$command\n"
                send_user "\n\n"
                                        }
            }
       }

send "exit\n"
send "exit\n"

send_user "#####################################\n"
send_user "#######  END $element  ########\n"
send_user "#####################################\n"
send_user "\n\n\n"

close
wait
}

Thanks!
scott

ps; I realize my indenting of the curly braces and other 
things are not standard...  :)