init.el

(defun winny/raise-or-create-window-system-frame (display)
  "Raise an existing frame in the window system or create a new one."
    (let ((frames (seq-filter #'(lambda (f) (frame-parameter f 'display)) (frame-list))))
      (if (null frames)
          (make-frame `((window-system . x)
                        (display . ,display)))
        (select-frame-set-input-focus (car frames)))))

raise-or-create-emacs.sh

#!/bin/sh

set -eu

emacsclient -n -e "$(printf -- '(winny/raise-or-create-window-system-frame "%s")' "$DISPLAY")"