linux-kernel - Re: [PATCH] scripts: dev-needs.sh: Enforce bash usage

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Date:   Thu, 10 Nov 2022 17:48:16 +0000
From:   Steffen Kothe <steffen.kothe@...the.de>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scripts: dev-needs.sh: Enforce bash usage

Am Wed, Nov 09, 2022 at 02:58:15PM -0800 schrieb Saravana Kannan:
> On Wed, Nov 9, 2022 at 9:04 AM Steffen Kothe <steffen.kothe@...the.de> wrote:
> >
> > Calling the script from a system which does not invoke bash
> > by default causes a return with a syntax error like:
> >
> >         ./dev-needs.sh: 6: Syntax error: "(" unexpected
> >
> > /bin/sh invokes on most distributions a symbolic link to a
> > default shell like dash (Debian) or bash (Ubuntu).
> >
> > Since the script depends on bash syntax, enforce the same by
> > default to prevent syntax errors caused by wrong shell type usage.
>
> I wrote this so that it can run on an Android target that runs toybox.
> Sadly toybox doesn't like have /bin/bash. This will break my use case.
> So I'll have to Nak this.

Ok, I see.

> I'm open to other ideas though as I'd like to this to work in as many
> cases as possible. Should we just add a wrapper that has /bin/bash and
> then sources this file?

I mean, we could leave at least a warning on top above the first
function via a simple echo.

Sth. like:

	echo "Warning: $0 is only tested for following shell variants
	      [toybox, bash]. Other shells might be not following the
	      specific syntax of this script."

	echo "Shell is: $(readlink /bin/sh)"

I would prevent to add another wrapper to it, because its fairly easy
to cp this file to a target. An embedded system with a pure POSIX compliant
shell will never be compatible to this kind of syntax.

What do you think about a more describing approach of the error instead
of handling it with some weird logic and wrapping?

Cheers,
	skothe

> Also looks like multiple #! lines aren't supported by bash, so we
> can't add multiple lines either.
>
> -Saravana
>
> >
> > Signed-off-by: Steffen Kothe <steffen.kothe@...the.de>
> > ---
> >  scripts/dev-needs.sh | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/scripts/dev-needs.sh b/scripts/dev-needs.sh
> > index 454cc304fb448..46537859727bc 100755
> > --- a/scripts/dev-needs.sh
> > +++ b/scripts/dev-needs.sh
> > @@ -1,4 +1,4 @@
> > -#! /bin/sh
> > +#! /bin/bash
> >  # SPDX-License-Identifier: GPL-2.0
> >  # Copyright (c) 2020, Google LLC. All rights reserved.
> >  # Author: Saravana Kannan <saravanak@...gle.com>
> > --
> > 2.30.2
> >
> >

--
Cheers,
	Steffen