Setting relative line numbers when in programming modes

Question

Looking to set relative line numbers when in programming modes. Looking through the older posts I see a way to set line numbers based on the mode - How do I display line numbers in emacs (not in the mode line)? :

@AnthonyB : (add-hook 'prog-mode-hook 'linum-mode)

Currently, use (setq-default display-line-numbers 'relative) in my init file for relative line numbers, however, would like to use this setting on a per mode basis partially all programming modes.

Answer 1

display-line-numbers is a buffer-local variable. To enable line numbers for only certain modes, do not use setq-default. Instead, use setq ... something like this:

(add-hook 'prog-mode-hook (lambda () (setq display-line-numbers 'relative)))

Or, use a preferred major-mode hook such as the perl-mode-hook or html-mode-hook:

(add-hook 'name-of-major-mode-hook (lambda () (setq display-line-numbers 'relative)))