What does "教えとくから" mean?


Found it here. <https://twitter.com/JINhktr/status/1141306368495742977>

> 酒の飲み方俺が教えとくから勘弁してやって

Is とくから a suffix or for 教え? Is it another word entirely? What does it mean?

I think it means something like "This is the way I've been taught to drink
sake, so forgive me."?

The 教えとくから part just confuses me since I haven't seen とく used like this
before.




The meaning is the same as if there was an "e" between "t" and "oku" i.e.
instead of saying 教えておく one says / it sounds and therefore one also writes
(not the "correct" writing, though) おしえとく.

This construction is not rude, but the omission of "e" comes from the
pronunciation (us being too lazy to articulate well).

