update_user_password_by_role.sh

#!/bin/bash                                                                                                                                    
drush sqlq "SELECT DISTINCT(SELECT name from users where uid = ur.uid) FROM users_roles AS ur WHERE ur.rid IN (4) LIMIT 50" | while read username;
do
   echo "Updating Password for Users $username"
   drush upwd $username --password='Pass@123'
   # or do whatever with individual element of the array
done