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Re: Should [[ -v 1 ]] be supported?

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  Re: Should [[ -v 1 ]] be supported? Martijn Dekker <martijn@inlv.org> - 2018-12-28 02:08 +0100

#14975 — Re: Should [[ -v 1 ]] be supported?

Op 28-12-18 om 01:39 schreef Peng Yu:
> What I meant in my original email is that I want something for testing
> if there is a command line argument (one or more, the exact number
> does not matter). $# gives more than that info, because it tells not
> only whether is any command line argument, but also how many. This
> could lead to slower performance if the goal is to just test if there
> is an argument.

I don't believe that at all. The number of positional parameters is kept 
anyway. It's not recalculated when you compare it to another number, so 
it's just as fast as a simple comparison of two integers.

> [[ -z ${1+s} ]] does something also more than necessary too, because
> it not only tests for whether $1 is set, it also replaced with a
> string "s". This also does more than just testing whether $1 is set.

That's negligible.

And even if it weren't -- if performance is *that* important to you, 
you're using the wrong language altogether.

- M.

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