ELisp: Save narrow-to-region

Emacs has a narrow-to-region command. [see Emacs: Narrow to Region]

The narrow-to-region is also very useful in elisp code. However, when you command is done, you should return to the narrow region state of the user before the command was called. Emacs lisp provides save-restriction for this purpose.

save-restriction

(save-restriction &rest BODY)

Execute BODY, then restoring any narrow-to-region in BODY.

;; preserve user's narrow-to-region
;; useful when you want to narrow-to-region in your code to work in just that region
(save-restriction
  (narrow-to-region pos1 pos2)
  ;; lisp code here
)

Positions (ELISP Manual)