Re: Incorrect example for `[[` command.

[Ilkka Virta]

On 21.9. 21:55, Dmitry Goncharov wrote:
> On Sat, Sep 21, 2019 at 12:34:39PM +0300, Ilkka Virta wrote:
> > [[:space:]]*?(a)b  isn't a well-defined POSIX ERE:
> >
> >     9.4.6 EREs Matching Multiple Characters
> >
> >     The behavior of multiple adjacent duplication symbols ( '+', '*', '?',
> >     and intervals) produces undefined results.
> >
> > https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/basedefs/V1_chap09.html
>
> This is unfortunate.
> *? and +? are widely used not greedy regexes.

In Perl-compatible regexes. Bash uses POSIX extended regular expressions.

And on a GNU system, while *? and +? don't give errors when used in an 
ERE, they still don't make the repetition non-greedy. They just act the 
same as a single * (as far as I can tell anyway).

 bash$ re='<.+?>'
 bash$ [[ "a<b>c<d>e" =~ $re ]] && echo $BASH_REMATCH
 <b>c<d>
 bash$ [[ "a<>e" =~ $re ]] && echo $BASH_REMATCH
 <>

--
Ilkka Virta / itvirta@iki.fi