Percentage sign in `print` and `message`

Question

I am trying to output

Humidity: 42% 

using both functions print and message. While print has no problem with the literal percentage sign, message throws a "Format string ends in middle of format specifier". What am I missing?

(defun demo()
  (interactive)
  (progn
    (setq text (format "Humidity: %s%%" 42))
    (print text)
    (message text)
    ))
(global-set-key (kbd "<f5>") 'demo)

Answer 1

By running (message (format ...)), you're using the string as a format twice.

print takes an object as its parameter, while message takes a format string. Use "%s" as the format and you can specify the string as the second optional argument to message:

(setq text (format "Humidity %s%%" 42))
(print text)
(message "%s" text)
  ⇒ "Humidity 42%"

or don't run format on text before sending it to message:

(setq value 42)
(setq format "Humidity %s%%")
(print (format format value))
(message format value)
  ⇒ "Humidity 42%"