linux-kernel - RE: [RFC PATCH 2/3] kconfig: allow to choose the shell for $(shell ) functions

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Date:   Fri, 19 Aug 2022 21:37:29 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Bagas Sanjaya' <bagasdotme@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>
CC:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Richard Purdie <richard.purdie@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Michal Marek <michal.lkml@...kovi.net>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH 2/3] kconfig: allow to choose the shell for $(shell )
 functions

From: Bagas Sanjaya
> Sent: 19 August 2022 09:59
> 
> On 8/19/22 13:56, Masahiro Yamada wrote:
> > GNU Make uses /bin/sh by default for running recipe lines and $(shell )
> > functions. You can change the shell by setting the 'SHELL' variable.
> > Unlike most variables, 'SHELL' is never set from the environment. [1]
> >
> > Currently, Kconfig does not provide any way to change the default shell.
> > /bin/sh is always used for running $(shell,...) because do_shell() is
> > implemented by using popen(3).
> >
> > This commit allows users to change the shell for Kconfig in a similar
> > way to GNU Make; you can set the 'SHELL' variable in a Kconfig file to
> > override the default shell. It is not taken from the environment. The
> > change is effective only for $(shell,...) invocations called after the
> > 'SHELL' assignment.
> >
> 
> Hmmm...
> 
> Can we say that if we run SHELL=/bin/bash make nconfig, Kconfig will use
> $SHELL but we can't set it as environment variable?

That just puts it into the environment for the single command.
You'd need to pass it as a command line argument to make.

(Or pass it in a different environment variable and then assign
it within the makefile.)

Or just remove the crappy bashisms and write portable shell scripts.
Just be glad you're not trying to use the SYSV /bin/sh.
(And avoid the other bugs that make dash fail to run most of the
scripts I write.)

Compex echo requests can be replaced by printf (without penalty
since it will be a shell builtin).

	David

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