Expect Script for Command Line

Question

I am writing a script that will allow a Linux admin to quickly change passwords of its users.

#!/usr/bin/expect
# Check password for strength 
# ----------------------------------------------
read -p "What's your username?" current_user
read -p "What's the root password?" pass
read -p "How many users?" num
COUNTER=0
         while [  $COUNTER -lt $num ]; do
         let index=COUNTER+1
             read -p "Enter username$index : " user_$index
             let COUNTER=COUNTER+1 
         done
read -p "Enter password : " password
echo 
echo "Tesing password strength..."
echo
result="$(cracklib-check <<<"$password")"
okay="$(awk -F': ' '{ print $2}' <<<"$result")"
if [[ "$okay" == "OK" ]]
then
    echo "PASSWORD ACCEPTED"
    echo "Modifying User Passwords..."
    COUNTER=0
         while [  $COUNTER -lt $num ]; do
             let index=COUNTER+1
             tmp=user_$index
             echo "Changing Password for " ${!tmp}
             echo ${!tmp}
             sudo passwd ${!tmp}
             expect -exact "[sudo] password for $current_user: "
             send "$pass\r"
             expect -exact "New password: "
             send "$password\r"
             let COUNTER=COUNTER+1 
         done

    #echo "$user:$password" | usr/sbin/chpasswd
else
    echo "Your password was rejected - $result"
        echo "Try again."
fi

However, the expect portion, which would automate the inputting of passwords, is not highlighted in my editor and does not work. I keep getting prompts to manually enter text. This is especially surprising since the script is sourcing expect, not bash. I've been trying to fix this for the past 2 hours. Can anyone please lend me a hand?

I don't understand what you're trying to do. It's declared like an expect script, but the body clearly isn't one. I suspect you've gone down the wrong path several steps ago, but I can't really tell from what you've presented where that was. — Michael Homer
– Michael Homer, Commented Sep 6, 2015 at 1:40

meuh · Accepted Answer · 2015-09-06 07:46:43Z

You are mixing expect and bash code. Your script is principally a bash script, so replace the top line by #!/bin/bash. Then replace the lines:

sudo passwd ${!tmp}
expect -exact "[sudo] password for $current_user: "
send "$pass\r"
expect -exact "New password: "
send "$password\r"

by a call to a function mychangepw with the args that expect needs, i.e. the current user, sudo password, user to change, and their password:

mychangepw $current_user "$pass" ${!tmp} "$password"

Add the function to the start of the script and use it to pass the args to expect, with the expect script on stdin upto the line "!":

mychangepw(){
    expect -d - "$@" <<\!
    set current_user [lindex $argv 0]
    set sudopass [lindex $argv 1]
    set user [lindex $argv 2]
    set password [lindex $argv 3]
    spawn sudo passwd $user
    expect -exact "\[sudo\] password for $current_user: "
    send "$sudopass\r"
    expect -exact "New password: "
    send "$password\r"
!
}

Be careful with the line starting "!". It must be the first and only char of the line, with no indent nor additional whitespace nor comments etc.

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