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From: Wolfgang Denk <wd@denx.de>
Subject: Re: [PATCH v2 0/2] env: setenv add resolve value option
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In-reply-to: <20211119043647.1251416-1-art@khadas.com>
References: <20211119043647.1251416-1-art@khadas.com>
Date: Fri, 19 Nov 2021 08:48:54 +0100
Message-ID: <2004466.1637308134@gemini.denx.de>
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To: Artem Lapkin <email2tema@gmail.com>
Cc: sjg@chromium.org, trini@konsulko.com, marek.behun@nic.cz, narmstrong@baylibre.com, twarren@nvidia.com, andre.przywara@arm.com, u-boot@lists.denx.de, u-boot-amlogic@groups.io, christianshewitt@gmail.com, art@khadas.com, nick@khadas.com, gouwa@khadas.com, Francis Laniel <francis.laniel@amarulasolutions.com>
List-ID: <u-boot-amlogic@groups.io>

Dear Artem,

In message <20211119043647.1251416-1-art@khadas.com> you wrote:
> Add possibility setup env variable with additional resolving vars insid=
e
> value.

Hm... if you want to evaluate variables, you should not prevent the
shell to do that by enclosing them in apostrophes?

> Usage examples:
>
> =3D> setenv a hello; setenv b world; setenv c '${a} ${b}'
> =3D> setenv -r d '${c}! ${a}...'
> =3D> printenv d
> d=3Dhello world! hello...

Without any new code added:

=3D> setenv a hello; setenv b world; setenv c ${a} ${b}
=3D> setenv d ${c}! ${a}...
=3D> printenv d
d=3Dhello world! hello...


I know very well that this does not cover all use cases you might
have in mind, as you speak of "deep resolve". But then, I'm first
missing an explanation (and documentation) of what "deep resolve"
actually means in this context, i. e. how many levels down you
evaluat.   Oh...  the code has "int max_loop =3D 32;" - this is a
limitation mentioned nowhere.  And are you really sure this is a
clever idea?  I am not convinced.  If we do something like this, we
should not invent a new non-standard way.  We should implement
standard shell behaviour instead (i. e. for example something like
the eval command).

> Artem Lapkin (2):
>   env: setenv add resolve value option
>   test: env: deep resolve value testing

This is one more of the patches that actually try to fix existing
problems with our ancient verion of the hush shell.  As far as I
understand, Francis (added to Cc:) has started working on an update
of hush to a current version.  We should rather help him with that
instead of implementing non-standard workarounds.

Best regards,

Wolfgang Denk

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