Re: [@]@A weird behaviour when IFS does not contain space

[Emanuele Torre]

On Wed, Jul 10, 2024 at 09:24:03AM -0400, Chet Ramey wrote:
> On 7/4/24 2:51 AM, Emanuele Torre wrote:
> > Hello.
> > 
> > Normally, ${foo[@]@A} expands to multiple values, that are the arguments
> > to run a declare command that sets foo to the current value/attributes.
> > 
> >      bash-5.2$ a=( abc xyz 123 ); declare -pa result=("${a[@]@A}")
> >      declare -a result=([0]="declare" [1]="-a" [2]="a=([0]=\"abc\" 
> > [1]=\"xyz\" [2]=\"123\")")
> >      bash-5.2$ a=( abc xyz 123 ); echoargs "${a[@]@A}"
> >      $1='declare'
> >      $2='-a'
> >      $3='a=([0]="abc" [1]="xyz" [2]="123")'
> > 
> > Today, I have noticed that if IFS is set to a value that does not
> > include space, [@]@A will expand to a single value
> 
> OK. Is that a problem? The man page says "when evaluated," and running the
> result through `eval' -- properly quoted -- produces the expected results.
> If there's an issue with making the expansion eval-safe, let's look at that.
> 
> -- 
> ``The lyf so short, the craft so long to lerne.'' - Chaucer
>                ``Ars longa, vita brevis'' - Hippocrates
> Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/
> 

I was curious about why it expands to multiple values if IFS is unset or
is set to a string that contains at least a ' ' character, but it
expands to a single value if IFS is set to any string that does not
contain any ' ' characters.
There is no obvious explanation for that, so that suggests there is
something weird going on with this particular kind of expansion.
"${a[@]@A}"

o/
 emanuele6