Making decisions on expect return

Question

I am trying to create an expect script which will send a different password string based on the "expect"

• Condition A: If a cisco device has not been setup with a username then the first prompt will simply be "Password:" - then it should use passwordA (no username)

• Condition B: If it has been setup with a username then the prompt will be "Username:" followed by "Password:" - then it should use Username and PasswordB

#!/bin/bash
# Declare host variable as the input variable
host=$1　
 # Start the expect script
(expect -c "
set timeout 20
# Start the session with the input variable and the rest of the hostname
spawn telnet $host
set timeout 3 
if {expect \"Password:\"} {
send \"PasswordA\"}
elseif { expect \"Username:\"}
send \"UsersName\r\"}
expect \"Password:\"
log_user 0 
send \"PasswordB\r\"
log_user 1
expect \"*>\"
# send \"show version\r\"
# set results $expect_out(buffer) 
#expect \"Password:\"
#send \"SomeEnablePassword\r\"
# Allow us to interact with the switch ourselves
# stop the expect script once the telnet session is closed
send \"quit\r\"
expect eof
")

Answer 1

You're doing it wrong. :)

The expect statement doesn't look to see what comes first, it waits until it sees what you ask for (and times out if it doesn't arrive in time), and then runs a command you pass to it. I think you can use it something like the way you're trying to, but it's not good.

expect can take a list of alternatives to look for, like a C switch statement, or a shell case statement, and that's what you need here.

I've not tested this, but what you want should look something like this:

expect {
  -ex "Username:" {
    send "UsersName\r"
    expect -ex "Password:" {send "PasswordB\r"}
  }
  -ex "Password:" {send "PasswordA\r"}
}

In words, expect will look for either "Username:" or "Password:" (-ex means exact match, no regexp), whichever comes first, and run the command associated with it.

---

In response to the comments, I would try a second password like this (assuming that a successful login gives a '#' prompt):

expect {
  -ex "Username:" {
    send "UsersName\r"
    expect -ex "Password:" {send "PasswordB\r"}
  }
  -ex "Password:" {
    send "PasswordA1\r"
    expect {
      -ex "Password:" {send "PasswordA2\r"}
      -ex "#" {}
    }
  }
}

You could do it without looking for the # prompt, but you'd have to rely on the second Password: expect timing-out, which isn't ideal.