(frame-list)
(#<frame *shell* 0x85e2ee0> #<frame *scratch* 0x8775cf8>)

(car (frame-list))
#<frame *shell* 0x85e2ee0>

(cdr (frame-list))
(#<frame *scratch* 0x8775cf8>)

(frame-pixel-height (cdr '(frame-list)))
(set-frame-height (car (frame-list)) 30)