This bach script makes separate backup files of all the databases in mysql and saves the result in the mysql_backup folder.

#!/bin/bash -v

USERNAME='yourusername'
PASSWORD='yourpassword'
HOSTNAME='yourhostname'
BackupFolder='/backup'

for i in $(echo 'SHOW DATABASES;' | mysql --user $USERNAME -p$PASSWORD -h $HOSTNAME | grep -v '^Database$' ); do
        mysqldump --user $USERNAME -p$PASSWORD -h $HOSTNAME --opt $i > $BackupFolder/$i.sql;
done;

Remember to change the -h, -p and -h switch according to your needs and avoid space between -p and the password variable.