GNU bug report logs - #33062
grep matches too lazily when invoked with -zoP and matching backreference followed by newline

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Johannes Riecken <johannes.riecken <at> gmail.com>
To: bug-coreutils <at> gnu.org
Subject: grep matches too lazily when invoked with -zoP and matching
 backreference followed by newline
Date: Tue, 16 Oct 2018 14:55:34 +0200

[Message part 1 (text/plain, inline)]

Dear maintainers:

*Bug summary: *GNU grep 3.0-2 matches too lazily when invoked with -zoP and
matching backreference followed by newline

*Steps to reproduce:*

Create file cases:

foo
bar
  cases:
    1: foo
    2: bar
baz
  cases:
    3: baz
quux

And run grep -zoP '(\s*)cases:\n(\1.*\n)*' cases

*Expected output:*

  cases:
    1: foo
    2: bar
  cases:
    3: baz

* Actual output:*

  cases:

  cases:

Best regards,

Johannes Riecken

[Message part 2 (text/html, inline)]

Message #8 received at 33062 <at> debbugs.gnu.org (full text, mbox):

From: Bernhard Voelker <mail <at> bernhard-voelker.de>
To: Johannes Riecken <johannes.riecken <at> gmail.com>, 33062 <at> debbugs.gnu.org
Subject: Re: bug#33062: grep matches too lazily when invoked with -zoP and
 matching backreference followed by newline
Date: Wed, 24 Oct 2018 01:16:57 +0200

reassign 33062 grep
stop

On 10/16/18 2:55 PM, Johannes Riecken wrote:
> Dear maintainers:
> 
> *Bug summary: *GNU grep 3.0-2 matches too lazily when invoked with -zoP and
> matching backreference followed by newline
> 
> *Steps to reproduce:*
> 
> Create file cases:
> 
> foo
> bar
>   cases:
>     1: foo
>     2: bar
> baz
>   cases:
>     3: baz
> quux
> 
> And run grep -zoP '(\s*)cases:\n(\1.*\n)*' cases
> 
> *Expected output:*
> 
>   cases:
>     1: foo
>     2: bar
>   cases:
>     3: baz
> 
> * Actual output:*
> 
>   cases:
> 
>   cases:
> 
> Best regards,
> 
> Johannes Riecken

Thanks for the report, however, you reached the GNU coreutils mailing list,
while your report is for 'grep'.

I'm therefore reassigning this issue to the GNU 'grep' package.

Have a nice day,
Berny

Message #13 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Bernhard Voelker <mail <at> bernhard-voelker.de>
To: Johannes Riecken <johannes.riecken <at> gmail.com>, 33062 <at> debbugs.gnu.org,
 bug-grep <at> gnu.org
Subject: Re: bug#33062: grep matches too lazily when invoked with -zoP and
 matching backreference followed by newline
Date: Sun, 28 Oct 2018 11:31:26 +0100

On 10/28/18 8:32 AM, Johannes Riecken wrote:
>> On Wed, Oct 24, 2018 at 1:17 AM Bernhard Voelker <mail <at> bernhard-voelker.de <mailto:mail <at> bernhard-voelker.de>> wrote:
>> reassign 33062 grep
>> stop
>>> On 10/16/18 2:55 PM, Johannes Riecken wrote:
>>> Dear maintainers:
>>>
>>> *Bug summary: *GNU grep 3.0-2 matches too lazily when invoked with -zoP and
>>> matching backreference followed by newline
>>>
>>> *Steps to reproduce:*
>>>
>>> Create file cases:
>>>
>>> foo
>>> bar
>>>   cases:
>>>     1: foo
>>>     2: bar
>>> baz
>>>   cases:
>>>     3: baz
>>> quux
>>>
>>> And run grep -zoP '(\s*)cases:\n(\1.*\n)*' cases
>>>
>>> *Expected output:*
>>>
>>>   cases:
>>>     1: foo
>>>     2: bar
>>>   cases:
>>>     3: baz
>>>
>>> * Actual output:*
>>>
>>>   cases:
>>>
>>>   cases:
>>>
>>> Best regards,
>>>
>>> Johannes Riecken
>>
>> Thanks for the report, however, you reached the GNU coreutils mailing list,
>> while your report is for 'grep'.
>>
>> I'm therefore reassigning this issue to the GNU 'grep' package.
>
> Thank you, could you please tell me where I can check the progress of my bug report after the reassignment? I didn't see
> it in the archives of the bug-grep mailing list.
> 
> Best wishes,
> Johannes

Well, it's still in the same GNU bug tracker:
  https://bugs.gnu.org/33062
but it seems that the bug wasn't forwarded automatically to the
bug-grep mailing list, thus adding that list explicitly ... hoping that
this doesn't open another bug.

Have a nice day,
Berny

Message #19 received at 33062 <at> debbugs.gnu.org (full text, mbox):

From: Jim Meyering <jim <at> meyering.net>
To: johannes.riecken <at> gmail.com
Cc: 33062 <at> debbugs.gnu.org
Subject: Re: bug#33062: grep matches too lazily when invoked with -zoP and
 matching backreference followed by newline
Date: Sun, 28 Oct 2018 12:19:09 +0000

tags 33062 notabug
close 33062
stop

On Tue, Oct 16, 2018 at 2:42 PM Johannes Riecken
<johannes.riecken <at> gmail.com> wrote:
> *Bug summary: *GNU grep 3.0-2 matches too lazily when invoked with -zoP and
> matching backreference followed by newline
>
> *Steps to reproduce:*
>
> Create file cases:
>
> foo
> bar
>   cases:
>     1: foo
>     2: bar
> baz
>   cases:
>     3: baz
> quux
>
> And run grep -zoP '(\s*)cases:\n(\1.*\n)*' cases
>
> *Expected output:*
>
>   cases:
>     1: foo
>     2: bar
>   cases:
>     3: baz
>
> * Actual output:*
>
>   cases:
>
>   cases:

Thanks for the report.
However, this is not a bug.
The \s in your regexp matches the preceding newline, too, and that
forces the behavior you see.
I presume you wanted something like this:

$ printf '%s\n' foo bar '  cases:' '    1: foo' '    2: bar' baz '
cases:' '    3: baz' quux\
  | grep -zoP '( *)cases:\n(\1.*\n)*'
  cases:
    1: foo
    2: bar
  cases:
    3: baz

The adjusted regexp works because it accepts only spaces in the group.
Don't be tempted to allow TABs, but rather ensure the input is
expanded to use only spaces for indentation.

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