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From: Chet Ramey <chet.ramey@case.edu>
Newsgroups: gnu.bash.bug
Subject: Re: Incorrect example for `[[` command.
Date: Fri, 20 Sep 2019 14:39:48 -0400
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Approved: bug-bash@gnu.org
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To: Ilkka Virta <itvirta@iki.fi>, bug-bash@gnu.org
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Xref: csiph.com gnu.bash.bug:15384

On 9/20/19 9:30 AM, Ilkka Virta wrote:
> On 20.9. 15:48, Greg Wooledge wrote:
>> but after the regex-glob-thing, it says:
>>
>>    That means values like ‘aab’ and ‘ aaaaaab’ will match
>>
>> So there's a shift in intent between a? and a+ in what's supposed to be
>> a regular expression.  Although of course the sentence is *literally*
>> true because the regex would be unanchored, and therefore it's sufficient
>> to match only the 'ab', and the rest of the input doesn't matter.
>> But that's just confusing, and doesn't belong in this kind of document.
> 
> It goes on to say "as will a line containing a 'b' anywhere in its value",
> so the text does recognize the zero-width-matching parts don't affect what
> matches. (I suppose they would affect what goes to BASH_REMATCH[0], but the
> text doesn't mention that.)

The portion of the manual before the example explains BASH_REMATCH and
BASH_REMATCH[0]. It also says "a sequence of characters in the value..."
when describing the pattern. This is the usual behavior of regcomp/regexec
(and grep/egrep, for that matter, since grep will print lines when a
substring matches the supplied pattern).

> I think it would be a better example with the anchored version also
> presented for comparison.

How about saying you can anchor the match with the usual ^ and $ special
pattern characters?

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
		 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/