Print the same string of text in all the available fixed width (mono spaced) fonts in a new Emacs buffer

compare-monospace-font-families-linux.el

;; See the following for more details
;;     https://emacs.stackexchange.com/a/50215/8887
;; and also see the following on a recent GNU/Linux or similar system:
;;     /usr/share/doc/fontconfig/fontconfig-user.html
;; for the explanation of spacing=100
;; also see the following UNIX StackExchange answer:
;;    https://unix.stackexchange.com/a/363368/13105
(defun compare-monospace-font-families ()
  "Display a list of all monospace font faces. Tested on GNU/Linux."
  (interactive)
  (pop-to-buffer "*Monospace Fonts*")
  (erase-buffer)
  (dolist (font-name (seq-filter (lambda (font)
                                   (when-let ((info (font-info font)))
                                     (string-match-p "spacing=100" (aref info 1))))
                                 (font-family-list)))
    (insert
     (propertize
      (concat "1 l; 0 O o [ < = > ] " font-name ")\n")
      'font-lock-face `((:family
                         ,(format "%s" (font-get (font-spec :name font-name) :family))))))))