Date: Thu, 20 Apr 2000 10:15:18 +0200 From: Martin Cracauer <cracauer@cons.org> To: Christian Weisgerber <naddy@mips.rhein-neckar.de> Cc: Cy.Schubert@uumail.gov.bc.ca, freebsd-arch@freebsd.org Subject: Re: Shells Message-ID: <20000420101518.B14732@cons.org> In-Reply-To: <200004160306.FAA67856@bigeye.rhein-neckar.de>; from naddy@mips.rhein-neckar.de on Sun, Apr 16, 2000 at 05:06:01AM %2B0200 References: <200004152356.e3FNup102274@cwsys.cwsent.com> <200004160306.FAA67856@bigeye.rhein-neckar.de>
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In <200004160306.FAA67856@bigeye.rhein-neckar.de>, Christian Weisgerber wrote:
> (Are shell wars really appropriate to -arch?)
>
> In article <200004152356.e3FNup102274@cwsys.cwsent.com> you write:
>
> > With commit of tcsh, I'd like to raise another question. Are there any
> > plans to replace sh with bash. Granted they're not 100% compatible,
> > though my only experience with bash vs sh incompatibility was over 6
> > years ago on a Linux system,
>
> bash is reputed to execute scripts rather slowly. I don't know if
> this still holds true for the current version. It definitely is
> rather large, though.
bash2 is large, but I cannot support the slowness claim. I pushed lot
of things through our sh and bash2 while fixing our sh and I never
noticed bash2 being slow. I didn't do benchmarks and I don't beleive
in benchmarks anyway, though.
> (Side note:
> Incompatibilities between bash and sh fall into two categories:
> 1. Comparing a POSIX shell (bash) with a traditional Bourne shell.
> This is a non-issue since our sh is a POSIX shell, too.
I did a lot of testing, and bash2 is by far the most bugfree
implementation of a bourne shell as specified by POSIX I found.
> 2. General upwards compatibility issues, i.e. the existence of
> additional pre-defined variables, commands, etc in the name
> space. This was already rare those six years ago, and as Linux
> has become _a_, if not _the_ major unix platform since, any
> offending scripts have been fixed.
bash2 is supposed to turn off extensions when called as 'sh'. I
didn't investigate how thoroughly this is done.
But in general I agree with your point: our /bin/sh should be a pure
POSIX shell without extension unless you turn them on. If you
replaced our /bin/sh with bash2, the first problem would be a manpage
that describes the POSIX part of bash only, but tracks new bash2
development.
> I don't think replacing sh by bash is an issue. If there's a
> question, then that's whether bash should be _added_ alongside sh.
> Note that bash's license (GPL) makes an inclusion into the tree
> unattractive.
>
> Personally, I think the addition of a _Korn shell_ should be worth
> some consideration. Candidates are pdksh, which is of similar size
> to our sh and could quite possibly replace it as well (as done on
> OpenBSD), or maybe ksh93, if AT&T's license should allow this.
>
> Some facts:
> * {,/usr}/bin/ksh is widely provided on commercial unices and is
> actually ksh88 there.
I think there is no point in going to /bin/ksh compatibilty now that
POSIX specifies the feature set of /bin/sh.
/bin/sh is the thing that is in the standards, not /bin/ksh.
Also, we have a hard time approaching the standard for /bin/sh. Doing
the same for /bin/ksh would be *additional* effort, as we can't drop
supporting /bin/sh when setting for /bin/ksh.
> * pdksh implements a substantial subset of ksh88, with some deviations
> for POSIX compatibility. It is in the public domain(!).
As I said in a different message, I think our current sh makes a
better /bin/sh than ksh does.
> * ksh93 implements a superset of ksh88, with some deviations for
> POSIX compatibility. It is under AT&T's open source(?) license
> <URL:http://www.research.att.com/sw/license/ast-open.html>.
> (If anybody has managed to actually understand this thing, please
> provide details.)
> * NetBSD uses pdksh for /bin/ksh (and a relative of our sh for
> /bin/sh).
> OpenBSD uses pdksh for /bin/sh and /bin/ksh.
As I said, I see no point in adding to confusion by supporting
/bin/ksh as the standard scripting shell. /bin/sh is what gets
polished by POSIX.
ksh is well placed in ports.
Martin
--
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Martin Cracauer <cracauer@cons.org> http://www.cons.org/cracauer/
BSD User Group Hamburg, Germany http://www.bsdhh.org/
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