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Re: Zero-length indexed arrays

From: Lawrence Velázquez
Subject: Re: Zero-length indexed arrays
Date: Wed, 22 Dec 2021 00:12:04 -0500
User-agent: Cyrus-JMAP/3.5.0-alpha0-4525-g8883000b21-fm-20211221.001-g8883000b

On Tue, Dec 21, 2021, at 10:48 PM, Dale R. Worley wrote:
> Lawrence Velázquez <vq@larryv.me> writes:
>> Did you mean to say that ${#FOO[*]} causes an error?  Because
>> ${FOO[*]} does not, a la $*:
> The case that matters for me is the Bash that ships with "Oracle Linux".
> Which turns out to be version 4.2.46(2) from 2011, which is a lot older
> than I would expect.  But it *does* cause an error in that verison:
>     $ ( set -u ; FOO=() ; echo "${FOO[@]}" )
>     bash: FOO[@]: unbound variable
>     $ bash -uc ': "${FOO[*]}"'
>     bash: FOO[*]: unbound variable
>     $ 
>> Like ${FOO[*]}, ${FOO[@]} and $@ are exempt from ''set -u''.
> It looks like that's a change since 4.2.46.

Yes, it appears to be from 4.4.


    This document details the changes between this version,
    bash-4.4-rc2, and the previous version, bash-4.4-beta2.


    3.  New Features in Bash

    a.  Using ${a[@]} or ${a[*]} with an array without any assigned
        elements when the nounset option is enabled no longer throws
        an unbound variable error.

> Is there text in the manual page about that?

I don't know.


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