Re: built-in regex matches wrong character

[Eric Blake]

On 09/06/2018 09:17 AM, Chet Ramey wrote:
> On 9/5/18 4:39 PM, Eric Blake wrote:
>
> > Or, you can use bash's 'shopt -s globasciiranges' which is
> > supposed to enable Rational Range Interpretation, where even in non-C
> > locales, a character range bounded by two ASCII characters takes on the C
> > locale definition of only the ASCII characters in that range, rather than
> > the locale's definition of whatever other characters might also be
> > equivalent (actually, while I know that shopt affects globbing, I don't
> > know if it also affects regex matching - but if it doesn't, that's probably
> > a bug that should be fixed).
>
> Since bash uses the C library's regexp engine, and most C libraries don't
> implement RRI, much less expose it as a flags option available via
> regcomp(), there's no reason to expect that globasciiranges would have
> any effect on regular expression matching.

But bash could be taught to convert any regex that contains a range with 
both endpoints ASCII into a different bracket expression before handing 
things over to regcomp().  That is, if the user is matching against 
[a-d], bash hands [abcd] to regcomp() instead.  You don't need a flag in 
regcomp() to get RRI, just merely some pre-processing (and often memory 
allocation, as the expansion of a range into a non-range tends to 
require more characters).

--
Eric Blake, Principal Software Engineer
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