There is the only flag for rubocop

Rubocop is a great tool to keep you code consistent, sane and informs you about some performance pitfalls.

Lately, I wanted to slowly add rubocop to an existing codebase. Rubocop has the -a parameter – which is short for --auto-correct – which corrects all the offenses. Having a thousand offenses and trying to auto fix them all, will generate quite the Pull Request. But there is also the --only parameter that allows you to check (and fix) only some or one type of offense.

So a neat way to add all the missing magic frozen_string_literal: true comments everywhere, might look like:

rubocop --only Style/FrozenStringLiteralComment -a