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 firstname.lastname@example.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,
> > 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
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?
Oddly enough, it looks like Windows might support #! somehow, see
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.