Programmatically Check MySQL's Option Values (key_buffer_size, innodb_buffer_pool_size, etc.)

Question

Is it possible to programmatically (via. the SQL interface, a CLI tool, etc) check the values of options that are normally set in a MySQL server's my.cnf file?

I have a suspicion that the server I'm using is reading the incorrect configuration file, and I'd like to be able to check what the values are actually set to.

Answer 1

You can access them via SELECT statements since they are exposed as global system variables.

SELECT @@key_buffer_size;
SELECT @@innodb_buffer_pool_size;

-- With a column alias you can use when fetching an associative array in PHP
mysql> SELECT @@key_buffer_size as keybufsize;
+------------+
| keybufsize |
+------------+
|    8388608 |
+------------+

You can, obviously, do this via PHP or the CLI, or whatever.