[[ ]]

[[ expression ]]

Korn shell only. Same as test expression or [ expression ], except that [[ ]] allows additional operators. Word splitting and filename expansion are disabled. Note that the brackets ([ ]) are typed literally, and that they must be surrounded by whitespace.

Additional Operators

&&	Logical AND of test expressions (short circuit).
||	Logical OR of test expressions (short circuit).
<	First string is lexically "less than" the second.
>	First string is lexically "greater than" the second.