whether to doUsed in the pattern -(으)ㄴ/는 건지 to ask or wonder what, how, or whether someone did or will do something. 할 건지 specifically refers to what someone will do or whether they will do it.
KO: 이번 주말에 뭘 할 건지 정했어?
EN: Have you decided what you’re going to do this weekend?