All Options and Variables have values (NULL values are not allowed), and all values have a generic type. Value types are similar to, but simpler than, the SQL language Data Types.
Currently, options’ value types are not documented, but most options clearly imply their value type.
Numeric values are positive or negative integers. Some numeric values are constrained, which means that the value must be within a specific range. Currently, constraints are not documented, but setting a variable out-of-range will cause an error.
String values are any kind of quoted strings. Since NULL values are not allowed, empty strings are sometimes used to mean “no value” or “undefined”.
When setting a variable, boolean values are one of the various true and false values listed for the BOOLEAN Data Type. When setting Boolean Options, no value is need or allowed.
Size values are like numeric values but allow optional size suffixes: K, M, and G. The size value 1k is equivalent to the numeric value 1024. Size values are shown as their equivalent numeric values when you query the variables.
Path values that are not absolute are prefixed with a path in the Drizzle installation directory. For example, if --pid-file is set to drizzled.pid, Drizzle prefixes that value with the --datadir value, resulting in a value like /opt/drizzle/data/drizzled.pid.
If an option has a default value, drizzled --help gives it in parentheses after arg, like (=drizzled-queries.log). The relevant documentation for an option should also list its default value, if any.