From: "René Neumann" <lists@necoro.eu>
To: zsh-users@zsh.org
Subject: Re: [Review Request] Arrays and their usage
Date: Mon, 31 May 2021 22:04:44 +0200 [thread overview]
Message-ID: <1eb8dc21-eb40-cc32-4ca8-c049d7273a03@necoro.eu> (raw)
In-Reply-To: <20210531173651.2pfklkhv5zizfldg@chazelas.org>
> Here's my take on answering this (repeating some of what has
> already been said).
Greatly appreciated!
> First, I'd say: `...` form of command substitution should really
> be banned these days. That's really a broken heritage from the
> Bourne shell. There's not good reason to keep using it these
> days. The main problem with it is the handling of backslash
> inside it (and the awkward nesting and the fact that it's less
> legible, etc...).
Fun fact: I prefer `...`, because I find it more legible, especially in
the x=`cmd y z` form¹. But TIL, that `` and $() are not interchangable.
Up to now, I thought the one is syntactic sugar for the other.
> The sed command could be written:
>
> sed -n 's/pkgname = //p'
Good catch, thanks
> Then, leaving `...` (or the better $(...)) unquoted performs
> IFS-splitting, so you're left with the same kind of conundrum as
> you get in POSIX shells when you leave any form of expansion
> ($param, $((arith)) as well there!) unquoted though at least
> zsh doesn't perform globbing there:
>
> [...]
>
> pkgs=(
> ${(f)"$(
> makepkg --printsrcinfo |
> sed -n 's/pkgname = //p'
> )"}
> )
Thank you for this detailed explanation. Not relying on IFS seems a good
thing to do, although the rest of the script probably does here and there².
Also thanks for this example of code structuring. /me likes.
(NB though: The linebreak for the two pipe elements was inserted for
this email only, with me hoping, that backslash newline was the correct
thing to do ;))
> The more idiomatic zsh variant to that ksh syntax would be:
>
> pkgs=( $DATABASE/$^pkgs )
>
> (same as rc's pkgs = ( $DATABASE/$pkgs )).
What does 'rc' stand for?
Again, thanks for this effort!
- René
¹ Longer story: $() is easily confused with ${}. Also, `...` is more "in
the background" and I let my highlighting make it clear to me, that I'm
in a subcommand. I would always prefer $() in large complex expressions
though, because.
² Although one could argue that setting IFS to something else than $'\n'
WILL break a lot of stuff, so one can expect it to be sane.
next prev parent reply other threads:[~2021-05-31 20:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-30 23:24 René Neumann
2021-05-31 0:28 ` Mikael Magnusson
2021-05-31 4:24 ` Bart Schaefer
2021-05-31 19:41 ` René Neumann
2021-05-31 17:36 ` Stephane Chazelas
2021-05-31 20:04 ` René Neumann [this message]
2021-05-31 21:42 ` Bart Schaefer
2021-05-31 21:43 ` Lawrence Velázquez
2021-05-31 22:05 ` René Neumann
2021-06-01 5:59 ` Stephane Chazelas
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