Green’s Dictionary of Slang

how’s by you? phr.

(US) a greeting.

1932		J. O’Hara ‘Mr. Cass and the $10,000’ in New Yorker 25 June 53/2: [H]e was vaguely polite. ‘How’s everything by you, Cass?’.
1968		K. Brasselle Cannibals 105: ‘Hiya, Virgil boy, how’s by you?’ ‘Same old jungle.’.
1970		D. Ponicsan Last Detail 71: ‘So how’s by you in the navy?’ ‘Same old crud.’.
1989		G. Cagle Payola! 235: Everything’s fine. How’s by you?
1991		W. Sonzski Fatal Ambition 130: ‘How’s by you?’ ‘Good, Sergeant,’ she said, with a pretty smile. ... ‘And how’s by you?’.
2005		J.W. Houghton Rough Magicke 152: ‘How’s by you?’ ‘Oh, okay, I guess.’.