Hive query regexp_extract

Question

I am trying to extract the ip address from "[223.104.227.42]". I want to extract the 223.104.227.42 between '[' and ']', Im using this query:

select regexp_extract('[223.104.227.42]', '$$(.*?)$$')

But I get an error:

FAILED: In function regexp_extract, pattern must has one group reference at least.

user_2700344 · Answer

Try to specify capturing group index as a parameter (1):

hive> select regexp_extract('[223.104.227.42]', '$$(.*?)$$',1);
OK
223.104.227.42
Time taken: 0.294 seconds, Fetched: 1 row(s)