Mandating path of POSIX-compliant shell? (was: Re: #! -- reconsideration?)
(Note to Austin folks: I'm cc'ing this to the LSB list since they
are working on a standard for Linux which will mandate things
like the location and properties of /bin/sh.)
(Note to LSB folks:
The Austin Common Standards Revision Group (CSRG) is a joint technical
working group established to consider the matter of a common revision
of ISO/IEC 9945-1, ISO/IEC 9945-2, IEEE Std 1003.1, IEEE Std 1003.2 and
the appropriate parts of the Single UNIX Specification.)
Donn Terry wrote in austin-group@opengroup.org:
> When I first saw the proposal to restore #!, I thought
> it was a good idea. I'm now caught up in a discussion
> about the path to the shell in the gcc list (the key
> elements are attached). #! is closely tied to the path
> to the shell (or rather its lack). I recognize that
> the "system configuration" discussion addresses the
> problem, if a bit obliquely. However, as you can
> infer from the mail discussion, the very bright (if
> sometimes opinionated, but aren't we all) folks in
> gcc land are having problems finding the POSIX shell,
> and thus aren't using it.
> ...
> I believe that #! as it currently stands will only help
> make this situation worse: building the pathname to a
> shell into scripts will tend to lock in particular pathnames,
> and very much in particular, the minimal Bourne shell.
>
> I see two solutions to this, neither of which I really like:
> 1) Change #! so it in some way honors some sort of user-controlled
> path analog. (Don't ask me how... I can imagine all sorts of
> things but they all give me the twitches.)
> 2) Require that all systems claiming conformance to the standard
> provide one command in ALL environments that lets the user bootstrap
> into a conforming environment.
Musing on this problem, I guessed that '/bin/posixsh' was a reasonable
name for the posix-compliant shell, and did a web search for posixsh.
http://www.debian.org/Lists-Archives/lsb-spec-9812/msg00003.html is a
related thread. One message in that thread,
http://www.debian.org/Lists-Archives/lsb-spec-9812/msg00022.html says:
> > If we decide that /bin/sh is an XPG3 shell, then we need to decide
> > where the POSIX confirming shell will be placed. The options include:
> >
> > /bin/posixsh (or another name, would be ugly if used for more programs)
> > /usr/xpg4/bin/sh (Solaris)
> > /usr/posix/bin/sh
> > /opt/posix/bin/sh
>
> I'd favour /usr/posix/bin/sh
> since there may be other utilities where there is a clash
> with existing behaviour that we deem serious enough to
> support two different versions.
Alan Cox seemed to favor /bin/posixsh in
http://www.debian.org/Lists-Archives/lsb-spec-9812/msg00012.html
Following Solaris's lead with xpg4, /usr/posix/bin/sh seems like a reasonable
proposal. What do the LSB folks think about this?
Is it beyond the scope of the Austin group to suggest this practice?
- Dan
p.s.
Oddly enough, it looks like Windows might support #! somehow, see
http://sourceware.cygnus.com/ml/cygwin/1999-05/msg00389.html
p.p.s.
For reference, http://www.freestandards.org/ has a link to the
relevant Linux standards that will specify location of shells.
--
Entia non sunt multiplicanda praeter necessitatem.
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