Extract string using rex

[RVDowning]

I have data that looks like:
20140609 19:14:03 [PERF] [CREATE PLAN START] Action=CreatePlan,
and would like to extract the text between the second pair of brackets, namely in the above line the text "CREATE PLAN START."

I tried rex field=_raw "]s+[=(?[]])" but obviously this isn't right.

[RVDowning · Accepted solution]

Finally got it right:

rex field=_raw "] [(?.+?)]"

[aweitzman]

This looks like it might work for you:

rex field=_raw "]\s+\[(?<step>[\w\s]*)\]"