linux-kernel - Re: [Question] Why CONFIG

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Message-ID: <20140609114010.GA28767@ravnborg.org>
Date:	Mon, 9 Jun 2014 13:40:10 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Masahiro Yamada <yamada.m@...panasonic.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-kbuild@...r.kernel.org
Subject: Re: [Question] Why CONFIG_SHELL

On Mon, Jun 09, 2014 at 07:25:48PM +0900, Masahiro Yamada wrote:
> Hi Sam,
> 
> 
> On Mon, 9 Jun 2014 09:49:35 +0200
> Sam Ravnborg <sam@...nborg.org> wrote:
> 
> > On Mon, Jun 09, 2014 at 02:04:12PM +0900, Masahiro Yamada wrote:
> > > Hi experts.
> > > 
> > > I think all the macros with CONFIG_ prefix are supposed to be
> > > defined in Kconfig.
> > > But I've been long wondering why there exists one exception:
> > > CONFIG_SHELL.
> > > 
> > > Is there any historical, or special reason?
> > It has been like this as far back as I remmeber.
> > I assume that one has planned to set the shell in Kconfig back then.
> >  
> > > Is it good to rename it to KBUILD_SHELL or something else?
> > Please do so, to free up the CONFIG_ namespace.
> > 
> > I the end Michal will decide if he want this cleanup.
> > On the top of my head I see no problems in doing this,
> > but maybe there are some out-of-tree modules or similar
> > we need to consider...
> 
> Thanks for your commet.
> 
> Another question popped up.
> 
> 
> CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \
>           else if [ -x /bin/bash ]; then echo /bin/bash; \
>           else echo sh; fi ; fi)
> 
> 
> If  bash is not found on the system,  CONFIG_SHELL falls back to  "sh".
> 
> Does it mean,  all shell scripts are written as  sh-compatible ?
Not all - but most.
All shell scripts that are invoked with $(CONFIG_SHELL) must be sh-compatible,
or in practice dash compatible as well as bash compatible.
The preference is bash as expressed with the above code.

	Sam
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