IF

There are two forms of the IF syntax. The first allows the conditional execution of one command:

IF condition singlecommand
IFNOT condition singlecommand

The second allows conditional execution of multiple commands within a block:

IF condition1 THEN
   ...
ELSE IF condition2 THEN
   ...
ELSE IFNOT conditionn THEN
   ...
ELSE
   ...
END

Note that only IF clause mandatory, all other clauses are optional. Both command forms IF and IFNOT can be used. Empty clauses (i.e., clauses without commands) are allowed. The last clause must be closed with an END statement. For more information on conditions see Conditional Expressions.