MySQL :How to enable slow query logging in mysql server on Linux

How to Enable Slow Query Logging for MySQL Server on linux
**********************************************************

The Slow Query Logging is used to capture the queries which do not use indexes .
execute for long time which is defined by long_query_time.
By default the value for long_query_time is 10 seconds.

mysql -u root -p

show variables like '%slow_query_log%';

show variables like '%long_query_time%';

Output
******
mysql show variables like '%slow_query_log%';
+---------------------+-----------------------------+
| Variable_name | Value |
+---------------------+-----------------------------+
| slow_query_log | OFF |
+---------------------+-----------------------------+

mysql show variables like '%long_query_time%';
+-----------------+-----------+
| Variable_name | Value |
+-----------------+-----------+
| long_query_time | 10.000000 |
+-----------------+-----------+

Slow Query Log File in Linux system
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Defaul Location of Slow Query log file on Linux is /var/lib/MySQL.

slow-query-log=1
long_query_time=10

1. service mysqld stop

slow-query-log=1