--check, -c

Check the table for errors. This is the default operation if you specify no option that selects an operation type explicitly.

--check-only-changed, -C

Check only tables that have changed since the last check.

--extend-check, -e

Check the table very thoroughly. This is quite slow if the table has many indexes. This option should only be used in extreme cases. Normally, myisamchk or myisamchk --medium-check should be able to determine whether there are any errors in the table.

If you are using --extend-check and have plenty of memory, setting the key_buffer_size variable to a large value helps the repair operation run faster.

--fast, -F

Check only tables that haven't been closed properly.

--force, -f

Do a repair operation automatically if myisamchk finds any errors in the table. The repair type is the same as that specified with the --recover or -r option.

--information, -i

Print informational statistics about the table that is checked.

--medium-check, -m

Do a check that is faster than an --extend-check operation. This finds only 99.99% of all errors, which should be good enough in most cases.

--read-only, -T

Don't mark the table as checked. This is useful if you use myisamchk to check a table that is in use by some other application that doesn't use locking, such as mysqld when run with external locking disabled.

--update-state, -U

Store information in the .MYI file to indicate when the table was checked and whether the table crashed. This should be used to get full benefit of the --check-only-changed option, but you shouldn't use this option if the mysqld server is using the table and you are running it with external locking disabled.