Re: select problem

[Stephane Chazelas <Stephane_Chazelas@xxxxxxxx>]

On Sat, Jan 17, 2009 at 12:21:31PM +0100, Richard Hartmann wrote:
> On Sat, Jan 17, 2009 at 10:25, Stephane Chazelas
> <Stephane_Chazelas@xxxxxxxx> wrote:
> 
> > "select" is not standard (that is not in the POSIX sh, which
> > is the only standard you can expect both bash and zsh to conform
> > to (when called as "sh")) and is a kshism. It's also rather
> > useless as one can do the same thing easily without.
> 
> zsh is not fully POSIX compliant and afaik, there are no plans to
> ever make it that way, either. While zsh and POSIX agree most
> of the time, using zsh as your sh _will_ get you strange effects.
> 
> I don't have time to dig up more, but look at [1] and [2] for some
> examples.
[...]

None of the so called POSIX shells are fully conformant. AFAIK,
only AT&T ksh claims to be fully conformant. bash follows the
GNU or LSB standards when they conflict with POSIX (see for
instance echo -e that doesn't output -e). ash derivatives still
have some way to go. But all try to be as conformant as
reasonable (so long as their design choices allow and as long as
implementing a POSIX feature wouln't break backward
compatibility).

For instance, I've never come accross a shell implementation
that implements that (rather stupid IMO) POSIX feature that says
that: "PATH=; echo test" should output "echo: command not
found" (that is a built-in should only be invoked if a command
by that name is found in $PATH).

Still, I can't think of how a script could be reasonably made to
rely on that behavior, which is why it's not a problem that all
shells break POSIX conformance there, in a same way that running
a POSIX script with zsh (in sh emulation) generally isn't a
problem because it's only in corner cases that zsh is not
conformant. When a POSIX conformance issue is found by someone,
it is generally raised on this mailing list and most of the time
fixed (at least in sh emulation).

Having said that, I agree there's no much point of having zsh as
your POSIX sh.

-- 
Stéphane