Re: [PATCH?] Nofork and removing newlines

[Stephane Chazelas <stephane@chazelas.org>]

2024-03-06 20:53:28 -0800, Bart Schaefer:
[...]
> > "${ foo}" and ${ foo} having the same wordsplitting behavior but only
> > differing in stripping newlines feels a bit magical and weird.
> 
> One question (and sort of the point) is whether anyone would really
> notice.  If you put it in quotes you're expecting a literal result,
> and if you (for example) assign it unquoted to a scalar you're
> expecting it to "just work" the way assigning $(foo) would.  It's a
> bit unusual but it seems to preserve the principle of least surprise,
> and it uses the least amount of extra syntax.
> 
> On the other hand I'm not highly invested in this.  In the absence of
> this (no)quoting behavior, I've found I nearly always want ${=${ foo
> }} or ${(f)${ foo }}, each of which gives exactly the same result with
> or without trimming.
[...]

For ${=${ foo }} that depends on whether $IFS contains a
(non-doubled) newline or not.

Without trimming:

$ IFS=:
$ printf '<%s>\n' ${=${ getconf PATH }}
</bin>
</usr/bin
>

$ IFS=$'\n\n'
$ printf '<%s>\n' ${=${ seq 3 }}
<1>
<2>
<3>
<>

For (f), see also:

$ printf '<%s>\n' "${(f@)${ print -l 'a b' '' 'c d' }}"
<a b>
<>
<c d>
<>

Like with IFS=$'\n\n', those are typically the cases where you
do want to preserve empty lines.

In both cases, trimming one (and only one) newline character
would lead to a better behaviour. One exception would be in:

lines=( "${(f@)${ print -l '' }}" )

Where you'd get no line instead of one empty line. Though at the moment, you get:

$ lines=( "${(f@)${ print -l '' }}" )
$ typeset -p lines
typeset -a lines=( '' '' )

(2 empty lines) which is not better.

We'd need to have a way to treat the separator as *delimiter*
instead (as POSIX requires for IFS splitting despite the S in
IFS; both "delimiting" and "separating" have their use).

-- 
Stephane