Re: [bug #66460] A documentation correction regarding an array nameref???

[Andreas Kähäri]

On Tue, Nov 19, 2024 at 01:40:12AM -0500, Harry Clauson wrote:
> URL:
>   <https://savannah.gnu.org/bugs/?66460>
> 
>                  Summary: A documentation correction regarding an array
> nameref???
>                    Group: The GNU Bourne-Again SHell
>                Submitter: harryc
>                Submitted: Tue 19 Nov 2024 06:40:06 AM UTC
>                 Category: None
>                 Severity: 3 - Normal
>               Item Group: None
>                   Status: None
>                  Privacy: Public
>              Assigned to: None
>              Open/Closed: Open
>          Discussion Lock: Any
> 
> 
>     _______________________________________________________
> 
> Follow-up Comments:
> 
> 
> -------------------------------------------------------
> Date: Tue 19 Nov 2024 06:40:06 AM UTC By: Harry Clauson <harryc>
> I was surprised that the documentation for "declare -n" states:
> 
> "The nameref attribute cannot be applied to array variables."
> 
> This appears to be incorrect as I frequently pass arrays using a nameref to
> avoid the overhead of making a copy of large amounts of data.
> 
> For example:
> 
> ####################################################
> function doit {
>       local -n blahref=$1
>       echo ${blahref[2]} # displays z
>       blahref[2]=a
>       blahref[3]=b
>       return 0
> }
> 
> declare -a blah
> blah=(x y z)
> 
> echo ${blah[2]} # displays z
> 
> doit blah
>       echo ${blah[2]} # displays a
>       echo ${blah[3]} # displays b
> ####################################################
> 

The code above does not apply the nameref attribute to an array.

Applying the nameref attribute to an array would be doing this:

        $ declare -n ref[0]=a
        bash: declare: ref[0]: reference variable cannot be an array


> In addition, when browsing the internet I see many questions regarding how to
> pass an array by reference, and the answers do not mention simply using a
> nameref.  And if not using a nameref it appears that they are actually passing
> data by value which is inefficient, especially in the case of arrays.
> 
> This leads me to believe that users who have read the documentation are not
> using this valuable feature, nor are they passing it along to others when
> answering related questions.
> 
> Please let me know if I am missing something here or if the documentation
> should be corrected in this regard.
> 
> Thank you!
> 
> 
> 
> 
> 
> 
> 
> 
> 
>     _______________________________________________________
> 
> Reply to this item at:
> 
>   <https://savannah.gnu.org/bugs/?66460>
> 
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-- 
Andreas (Kusalananda) Kähäri
Uppsala, Sweden

.