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From: hk <hkadeveloper@gmail.com>
Newsgroups: gnu.bash.bug
Subject: Re: Incorrect example for `[[` command.
Date: Sat, 21 Sep 2019 20:47:52 +0800
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Approved: bug-bash@gnu.org
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References: <CAD0rTC7W20s7-8np7Z+CmZQczTQ+LX=Y1x01gAenewrpiJS5jw@mail.gmail.com> <8e7c8ea4-2fdf-4809-0b50-ea1bfbbec165@case.edu> <CAD0rTC68qoXvCV9SLP1dJ8Gvg71W7bg9yt8jjpmpESK-jKD7Wg@mail.gmail.com> <bf5a1810-8316-239c-0c5a-f85803048ab6@iki.fi> <CAD0rTC6H00cYrLU2zWa9jpexY9qH-07SHide1JdjN6Vpr4BHyg@mail.gmail.com>
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To: Ilkka Virta <itvirta@iki.fi>
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Thanks. Have learnt a lot from your replies.

On Sat, Sep 21, 2019 at 5:34 PM Ilkka Virta <itvirta@iki.fi> wrote:

> On 21.9. 03:12, hk wrote:
> > Thanks for the reply. I was wrong in my report. It does match values like
> > aab and  aaaaaab  in its original form.
>
> In some systems, yes. (It does that on my Debian, but doesn't work at
> all on my Mac.)
>
> > It is syntatically correct as a regular expression.
>
> [[: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
>
>
> --
> Ilkka Virta / itvirta@iki.fi
>