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Date: Thu, 15 Oct 2015 18:16:03 -0700
From: Ray Andrews <rayandrews@eastlink.ca>
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To: zsh-users@zsh.org
Subject: Re: backreferences
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 <151015161602.ZM30622@torch.brasslantern.com>
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On 10/15/2015 04:16 PM, Bart Schaefer wrote:

>      [[ "$sstring" = (#b)([^i]#inside)(*) ]]
Very good, I tried a few things and missed the one that works. But I'm 
finding out that
it's dangerous w.o. the test, since 'match' will remain silently 
unchanged if the
comparison fails.
> ... or it might mean that
> you're trying to not-match multiple characters in the tested string in
> a certain order.
Yes.

> In the latter case you want ^(string), or more often
> (^(string)), but you also must setopt EXTENDED_GLOB.
Sorry for the ambiguity.  Clarity in the mind of the sender and clarity 
in the mind
of the receiver are not the same thing.  I mean that the match should 
fail not on
meeting one character (or selection of characters), but it should fail 
on meeting
a specific sequence of characters:

    test ()
    {

    sstring="abcdeedcbaabcde"
    if [[ "$sstring" = (#b)([(^(edcba))]*)(edcba)(*) ]];

    then
           echo "you have a match"
    else
         match=
    fi

    echo "one   $match[1]"
    echo "two   $match[2]"
    echo "three $match[3]"
    }


     one   abcde
     two   edcba
     three abcde


I tried to learn how to do that with sed and never did get it figured out.
zsh can give us just about most of what we want anyway.  Pretty cool.

Thanks.