Re: capturing in ${VAR//(*(\/)(+([^\/]))?(\/)/_${BASH_REMATCH[1]}_}

2016-02-20 Thread Dan Douglas 
On Mon, Feb 8, 2016 at 9:20 AM, Stephane Chazelas
 wrote:
> 2016-02-08 09:00:09 -0500, Chet Ramey:
>> On 2/8/16 2:47 AM, Linda Walsh wrote:
>> > When you are doing a var expansion using the
>> > replacement format ${VAR//./.}, is there some way to
>> > put parens around some part of the expression and reference
>> > them as in the [[V~re]] RE-matches?
>>
>> No.  Shell patterns do not have backreferences.
> [...]
>
> Note that the feature is available in other shells and quite
> handy there. It could be worth adding to bash
>
> $ zsh -o extendedglob -c 'a=1234; echo 
> ${a//(#b)(?)(?)/${match[2]}${match[1]}}'
> 2143
> (#b) to activate back-references stored in $match array.
>
> $ zsh -o extendedglob -c 'a=1234; echo ${a//(#m)?/<$MATCH>}'
> <1><2><3><4>
> (#m) to record the matched portion in $MATCH.
>
> Though I suspect for bash you would prefer the ksh93 syntax:
>
> $ ksh93 -c 'a=1234; echo ${a//@(?)@(?)/\2\1}'
> 2143

Technically that's "grouping", but yeah it's a useful feature. ksh
does backrefs in plain shell patterns also.

$ ksh -c 'a=11223344; echo "${a//@(@(?)\2)@(@(?)\4)/\3\1}"'
22114433

Re: capturing in ${VAR//(*(\/)(+([^\/]))?(\/)/_${BASH_REMATCH[1]}_}

2016-02-08 Thread Stephane Chazelas 
2016-02-08 09:00:09 -0500, Chet Ramey:
> On 2/8/16 2:47 AM, Linda Walsh wrote:
> > When you are doing a var expansion using the
> > replacement format ${VAR//./.}, is there some way to
> > put parens around some part of the expression and reference
> > them as in the [[V~re]] RE-matches?
> 
> No.  Shell patterns do not have backreferences.
[...]

Note that the feature is available in other shells and quite
handy there. It could be worth adding to bash

$ zsh -o extendedglob -c 'a=1234; echo ${a//(#b)(?)(?)/${match[2]}${match[1]}}'
2143
(#b) to activate back-references stored in $match array.

$ zsh -o extendedglob -c 'a=1234; echo ${a//(#m)?/<$MATCH>}'
<1><2><3><4>
(#m) to record the matched portion in $MATCH.

Though I suspect for bash you would prefer the ksh93 syntax:

$ ksh93 -c 'a=1234; echo ${a//@(?)@(?)/\2\1}'
2143

-- 
Stephane

Re: capturing in ${VAR//(*(\/)(+([^\/]))?(\/)/_${BASH_REMATCH[1]}_}

2016-02-08 Thread Chet Ramey 
On 2/8/16 2:47 AM, Linda Walsh wrote:
> When you are doing a var expansion using the
> replacement format ${VAR//./.}, is there some way to
> put parens around some part of the expression and reference
> them as in the [[V~re]] RE-matches?

No.  Shell patterns do not have backreferences.


-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRUc...@case.eduhttp://cnswww.cns.cwru.edu/~chet/

capturing in ${VAR//(*(\/)(+([^\/]))?(\/)/_${BASH_REMATCH[1]}_}

2016-02-07 Thread Linda Walsh 

When you are doing a var expansion using the
replacement format ${VAR//./.}, is there some way to
put parens around some part of the expression and reference
them as in the [[V~re]] RE-matches?

Couldn't find anything in the manpage, but I could easily
have missed something...?

Thanks...