While exploring GRASS GIS and writing scripts to run its commands, I realized it would be way more convenient to have a shortcut for sending lines to the shell for evaluation. This, instead of copy-pasting each sentence from the script to the shell buffer (ugh).

Thanks to this answer on Stackoverflow, I was able to do just that with a minor tweak.

(defun sh-send-line-or-region (&optional step)
  (interactive ())
  (let ((proc (get-process "shell"))
        pbuf min max command)
    (unless proc
      (let ((currbuff (current-buffer)))
        (switch-to-buffer currbuff)
        (setq proc (get-process "shell"))
    (setq pbuff (process-buffer proc))
    (if (use-region-p)
        (setq min (region-beginning)
              max (region-end))
      (setq min (point-at-bol)
            max (point-at-eol)))
    (setq command (concat (buffer-substring min max) "\n"))
    (with-current-buffer pbuff
      (goto-char (process-mark proc))
      (insert command)
      (move-marker (process-mark proc) (point))
      (setq comint-scroll-to-bottom-on-output t)
    (process-send-string  proc command)
    (display-buffer (process-buffer proc) t)
    (when step 
      (goto-char max)

(defun sh-send-line-or-region-and-step ()
  (sh-send-line-or-region t))

And because I’ve set <s-return> to ess-eval-region-or-line-and-step, I set the same shortcut for sending commands to the shell for evaluation.

(require 'sh-script)
(define-key sh-mode-map (kbd "<s-return>") 'sh-send-line-or-region-and-step)

Et voila!