Extract string from brackets

Question

I\'m pretty new at bash so this is a pretty noob question..

Suppose I have a string:

string1 [string2] string3 string4

I would like

Answer 1

Here is an awk example, but I'm matching on parenthesis which also makes it more obvious of how the -F works.

echo 'test (lskdjf)' | awk -F'[()]' '{print $2}'