mysql slow queries log

mysql --version

version 5.5.52

emacs /etc/mysql/my.cnf

log_slow_queries = /var/log/mysql/mysql-slow.log
long_query_time = 5

version 5.7.17

emacs /etc/mysql/mysql.conf.d/mysqld.cnf

slow_query_log = /var/log/mysql/mysql-slow.log
long_query_time = 5