In case you want to install mysql or percona unattended (like in my case ansible), you can use following script:
# first part opens mysql log
# second part greps lines with temporary password
# third part picks last line (most recent one)
# last part removes all the line except the password
# the result goes into password variable
password=$(cat /var/log/mysqld.log | grep "A temporary password is generated for" | tail -1 | sed -n 's/.*root@localhost: //p')
# setting new password, you can use $1 and run this script as a file and pass the argument through the script
newPassword="wh@teverYouLikE"
# resetting temporary password
mysql -uroot -p$password -Bse "ALTER USER 'root'@'localhost' IDENTIFIED BY '$newPassword';"