#!/bin/bash
# your code goes here
cd /tmp
echo 'aaaa' > 1.txt
echo 'bgdgsgbsb' >> 1.txt
echo 'cccc' >> 1.txt
echo 'dddd' >> 1.txt
sed '
/b.*b/ {h;d}
$ {p;g}
' 1.txt
IyEvYmluL2Jhc2gKIyB5b3VyIGNvZGUgZ29lcyBoZXJlCgpjZCAvdG1wCmVjaG8gJ2FhYWEnID4gMS50eHQKZWNobyAnYmdkZ3NnYnNiJyA+PiAxLnR4dAplY2hvICdjY2NjJyA+PiAxLnR4dAplY2hvICdkZGRkJyA+PiAxLnR4dAoKc2VkICcKL2IuKmIvIHtoO2R9CiQge3A7Z30KJyAxLnR4dA==