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Comment by darrenf | Hacker News Reader

Regardless of `-a` vs two tests and `&&`, there's no need to shell out to `expr` if bash's arithmetic evaluation is available:

    [ $((1+1)) -eq 2 ]

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arithmetic evaluation is ((…)), $((…)) is arithmetic expansion.

There’s no need for test(1) / [(1) or conditional expressions ([[…]]) if you’re doing arithmetic:

if ((1+1 == 2)); then …; fi

Even better, and TIL. Thanks!

The fact that seasoned developers have to discuss how to write 1+1 correctly, says everything you need to know about the language.

I'm going to assume that if one is using [ rather than [[ then one will also want to use expr rather than $(()).

Arithmetic expansion is a feature of all POSIX compliant shells, which furthermore advises against using `expr`. The latter is only needed for non-compliant shells like some legacy implementations of the Bourne shell.

Oh, I did not know that! Thanks.

What's the basis for that assumption? I'm struggling to see a reason to not use the shell for arithmetic, regardless of `/usr/bin/[`, builtin `[` or `[[`.

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