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Re: Incorrect example for `[[` command.
From: |
hk |
Subject: |
Re: Incorrect example for `[[` command. |
Date: |
Sat, 21 Sep 2019 20:47:52 +0800 |
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
>