Re: bash tries to parse comsub in quoted PE pattern

[alex xmb sw ratchev]

On Wed, Oct 18, 2023, 14:20 Zachary Santer <zsanter@gmail.com> wrote:

> On Tue, Oct 17, 2023 at 5:56 PM Emanuele Torre <torreemanuele6@gmail.com>
> wrote:
>
> >     bash-5.1$ letters=( {a..z} ); echo "${letters["{10..15}"]}"
> >     k l m n o p
> >
>
> Then there's the question "Was that even supposed to work like that?" If
> so, you'd think it would generalize to being able to pass a series of
> whitespace-delimited indices to an array expansion.
>

by chet stating many times that every bash item undergoes expansion ..
like why [[ -v var[\$k] ]] .. cause $k once and if not \$ again in parsing
the bash cmd / keyword / whatever

In Bash 5.2:
> $ array=( zero one two three four five six )
> $ printf '%s\n' "${array["{2..6..2}"]}"
> two
> four
> six
> $ printf '%s\n' "${array[{2..6..2}]}"
> -bash: {2..6..2}: syntax error: operand expected (error token is
> "{2..6..2}")
> $ printf '%s\n' "${array["2 4 6"]}"
> -bash: 2 4 6: syntax error in expression (error token is "4 6")
> $ printf '%s\n' "${array[2 4 6]}"
> -bash: 2 4 6: syntax error in expression (error token is "4 6")
> $ printf '%s\n' "${array[2,4,6]}"
> six
> $ indices=(2 4 6)
> $ printf '%s\n' "${array[${indices[@]}]}"
> -bash: 2 4 6: syntax error in expression (error token is "4 6")
> $ printf '%s\n' "${array[${indices[*]}]}"
> -bash: 2 4 6: syntax error in expression (error token is "4 6")
>

u miss at least once the quotes of ['{blabla}']

Considering I don't think this is documented anywhere, and what's in
> between the square brackets gets an arithmetic expansion applied to it, I'm
> going to guess "no."
>
> So how important is it to maintain undocumented behavior?
>
> Why does "${#@}" expand to the same thing as "${#}"? Why is $[  ]
> equivalent to $((  ))? Does that stuff need to continue to work forever?
>

its both the 1+ args
$@ expands to different args
"$@" to preserve spacesafe

$* expands the same ( all args ) to one-arg
"$*" spaceaafe

Zack
>

x

>