The real culprit is glibc rather than coreutils, as it's the former which
defines collation rules.
> If not `LC_ALL=C` is set, the sort result is weird.
> Running it with `LC_ALL=C` everything is fine:
> > sort: using simple byte comparison
> > a-ab
> > ____
> > a-ac
> > ____
> > aac
> > ___
>
>
> But switching to en_US.UTF-8 or de_DE.UTF-8 I got the broken result:
> > sort: using
> > a-ab
> > ____
> > aac
> > ___
> > a-ac
> > ____
Yeah, this is indeed bogus. Years ago, I compared different libcs and
operating systems, with a sample that looks mostly at version numbers:
glibc, "real" language locales:
0 9
0.9.0
0.9.0-a0-foo-bar
({---=[ 0.9.0-a11 ]=---})
0.9.0-a17-quux
(0.9.0-a2)
0.9.0+a99-1
0.9.0-rc1
0.9.1
0 9 9
({---=[ 0.9-a11 ]=---})
0.9 ab
Windows:
(0.9.0-a2)
({---=[ 0.9.0-a11 ]=---})
({---=[ 0.9-a11 ]=---})
0 9
0 9 9
0.9 ab
0.9.0
0.9.0+a99-1
0.9.0-a0-foo-bar
0.9.0-a17-quux
0.9.0-rc1
0.9.1
glibc, C.UTF-8:
(0.9.0-a2)
({---=[ 0.9-a11 ]=---})
({---=[ 0.9.0-a11 ]=---})
0 9
0 9 9
0.9 ab
0.9.0
0.9.0+a99-1
0.9.0-a0-foo-bar
0.9.0-a17-quux
0.9.0-rc1
0.9.1
Ordering between . and - is debatable, sorting without any heed to symbols
is an obvious mistake. My guess is that someone took rules written for
19th-century printed dictionaries where symbols were a rare oddity, and
applied them to a computer setting where symbols do matter.
I agree with you that "a-a" must not sort same as "aa" -- this surprises
users and makes it hard to eyeball-search, which is the primary purpose for
human-locale sort.
> So any algorithm or script which depends on a stable sorted order will
> fail.
Well yeah, this should not differ between implementations. Different
languages do have different collation orders, though: most languages place
accented characters just after the base letter (or sometimes sorted as
same), but for example Swedish wants z<å. Thus, you must not assume the
order is stable between locales.
> As a mitigation I tried `LC_COLLATE=C` but still the ‘en_US.UTF-8’
> sorting rules will be used :-/
For this reason, I use LC_COLLATE=C.UTF-8, which works for me (do you
perhaps have LC_ALL, which overrides LC_COLLATE?). There's the issue of
case-sensitive sorting which is liked by hackers but not by normal people,
but otherwise, for an English language user, C.UTF-8 collation is
drastically better. An international user would want a<ą<b, though, which
makes C.UTF-8 inadequate here.
Meow!
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