Re: [Help-bash] Passing multiple arrays to a function

[Dmitry Alexandrov]

Greg Wooledge <address@hidden> wrote:
> On Wed, Feb 13, 2019 at 07:01:10PM +0300, Dmitry Alexandrov wrote:
>> safe-fn ()
>> {
>>     local a=("${!1}") b=("${!2}")
>>     local array_1=('FAIL')
>>     printf '%s;' "address@hidden" "address@hidden"
>>     printf '\n'
>> }
>> 
>> safe-fn 'address@hidden' 'address@hidden'
>
> Oh my gods, it's *THAT* hack again.

You mean indirectly addressing elements of array by its read representation 
(ref='arr[i]'; echo "${!ref}"), don’t you?

> I don't know where it came from (other than "try a bunch of shit and
> see if it works"), or how it got such a foothold in people's minds.

Alas, I cannot recall when and where exactly I personally learned this, but for 
past several years most people, I believe, get to known about it from your 
incredible collection of Bash hacks and tricks [1].

[1] https://mywiki.wooledge.org/BashFAQ/006?action=diff&rev1=24&rev2=23

> I have nothing good to say about that hack.  At some point a couple
> years ago, we asked Chet whether it was actually a supported thing,
> or whether a future bug-fix of the parser might make it stop behaving
> this way, and the answer was inconclusive.
>
> In any case, you are not using namerefs here, so my warnings about
> nameref collisions simply do not apply.

This is perfectly possible with namerefs as well:

#!/bin/bash

array_1=("PASS")
array_2=("1 foo" "2 foo")

nameref-safe-fn ()
{
    local -n a_ref=$1 b_ref=$2
    local a=("address@hidden") b=("address@hidden")
    local array_1=('FAIL')
    printf '%s;' "address@hidden" "address@hidden"
    printf '\n'
}

nameref-safe-fn array_1 array_2

PASS;1 foo;2 foo;

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