This is an extract from an online book:

Now that you have Git on your system, you’ll want to do a few things to customize your Git environment. You should have to do these things only once on any given computer; they’ll stick around between upgrades.

I know that should and have to are both modal verbs, and since have to is a phrasal modal, their combination is grammatical. But I'm not sure about the meaning of this combination. The combination sounds strange to me. The main usage of should is for saying what the correct thing to do is, and have to is usually used to express necessity.

There are combinations of modal verbs with clear meaning, for example in "You may not be allowed to enter that room." Here, may expresses possibility and be allowed to expresses permission. It's clear what is meant by the combination.

1 Answer 1


The modal "should" expresses expectation. The phrase "have to" expresses obligation: namely the obligation to do something to get a certain result.

So this means "I expect that you will be obliged to run these commands once but you will not be obliged to run them more than once".

  • LIke most modals, should has an epistemic meaning (about expectation and knowledge) as well as a deontic meaning (about obligation).
    – Colin Fine
    May 7 at 20:25

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