Re: have you ever mistyped [[:lower:]] as [:lower:] ?

[Eric Blake]

On 09/01/2010 08:09 AM, Paolo Bonzini wrote:
> On 09/01/2010 04:01 PM, Jim Meyering wrote:
> > > Do you honestly imagine
> > > http://opengroup.org/onlinepubs/007908775/xbd/re.html changed to say
> > > "If a bracket expression consists of a colon, a series of alphabetic
> > > characters, and another colon, the implementation's behavior is
> > > undefined?
> >
> > Perhaps that is where we disagree, then.
> > I do not require that POSIX allow the new behavior.
>
> That may be it. In particular, I think for something that POSIX is
> unlikely to aver allow, there should be another way than POSIXLY_CORRECT
> to disable it.

Personally, I'd _like_ to try to get POSIX to allow unspecified behavior 
for a bracket expression that starts and ends with colon, at which 
point, we could then drop the POSIXLY_CORRECT notion, and blindly reject 
[:upper:].  In fact, I'm going to go create that aardvark today (link to 
follow soon...)

But I'm happy with Jim's approach - to treat it as the valid regex which 
it is under current POSIX rules, set POSIXLY_CORRECT; otherwise, since 
it is so likely to be wrong, treat it as an error, and hope that POSIX 
will change to agree someday.

> > Ranges like [A-Z] are so common that changing the default
> > would have far-reaching effects. Will it ever be possible?
> > I don't know. Perhaps if we first allow it to be enabled via
> > some new environment variable, and then, much later, make it the default.
>
> /me whispers --warn...

I also see the value of adding a --warn parameter, to fine-tune how much 
warning is issued, and whether warnings are fatal.  But I'm also just 
fine waiting until we have more implementation experience (how often 
does the current warning trigger, what other expressions are worth 
warning about, and what does the Austin Group say about my proposed 
change to BRE and ERE bracket expressions).  In the meantime, not having 
a --warn is workable; I'm certainly not missing the fine-tune knob yet 
in my own usage patterns of grep.

--
Eric Blake   address@hidden    +1-801-349-2682
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