(use extras posix)

(define chicken-coop (or (get-environment-variable "CHICKENS") "~/chickens"))
(define chicken-link "use-this")

(define (fail msg . args)
  (apply fprintf (current-error-port) msg args)
  (newline (current-error-port))
  (exit 1))

(define (assert-chicken-coop-exists)
  (unless (and (file-exists? chicken-coop) (directory? chicken-coop))
    (fail "CHICKENS does not exist or is not a directory: ~S" chicken-coop)))