GNU bug report logs - #22071
incorrect behaviour for inverted matches with -l on empty files

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

From: Mark Wotton <mwotton <at> gmail.com>
To: bug-grep <at> gnu.org
Subject: incorrect behaviour for inverted matches with -l on empty files
Date: Tue, 01 Dec 2015 22:36:10 +0000

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

orb ➜  ~/src/grep-2.22  touch empty
orb ➜  ~/src/grep-2.22  ./src/grep -v -l "hi there" ./empty

gives empty output. Surely the file "empty" should match 'does not match
"hi there"' ?

cheers
mark

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

Message #8 received at 22071 <at> debbugs.gnu.org (full text, mbox):

From: Santiago Ruano Rincón <santiagorr <at> riseup.net>
To: Mark Wotton <mwotton <at> gmail.com>
Cc: 22071 <at> debbugs.gnu.org
Subject: Re: bug#22071: incorrect behaviour for inverted matches with -l on
 empty files
Date: Wed, 2 Dec 2015 13:56:48 +0100

El 01/12/15 a las 22:36, Mark Wotton escribió:
> orb ➜  ~/src/grep-2.22  touch empty
> orb ➜  ~/src/grep-2.22  ./src/grep -v -l "hi there" ./empty
> 
> gives empty output. Surely the file "empty" should match 'does not match
> "hi there"' ?
       -v, --invert-match
              Invert the sense of matching, to select non-matching lines.

I think this is not a bug because there isn't non-matching line in an empty file.

Cheers,

-- Santiago

Message #11 received at 22071 <at> debbugs.gnu.org (full text, mbox):

From: Mark Wotton <mwotton <at> gmail.com>
To: Santiago Ruano Rincón <santiagorr <at> riseup.net>
Cc: 22071 <at> debbugs.gnu.org
Subject: Re: bug#22071: incorrect behaviour for inverted matches with -l on
 empty files
Date: Wed, 2 Dec 2015 08:14:05 -0500

hm. "grep -l '' empty" also doesn't print anything, so I guess it's
consistent, at least.

On 12/2/15, Santiago Ruano Rincón <santiagorr <at> riseup.net> wrote:
> El 01/12/15 a las 22:36, Mark Wotton escribió:
>> orb ➜  ~/src/grep-2.22  touch empty
>> orb ➜  ~/src/grep-2.22  ./src/grep -v -l "hi there" ./empty
>>
>> gives empty output. Surely the file "empty" should match 'does not match
>> "hi there"' ?
>        -v, --invert-match
>               Invert the sense of matching, to select non-matching lines.
>
> I think this is not a bug because there isn't non-matching line in an empty
> file.
>
> Cheers,
>
> -- Santiago
>


-- 
A UNIX signature isn't a return address, it's the ASCII equivalent of a
black velvet clown painting. It's a rectangle of carets surrounding a
quote from a literary giant of weeniedom like Heinlein or Dr. Who.
        -- Chris Maeda

Message #14 received at 22071 <at> debbugs.gnu.org (full text, mbox):

From: Eric Blake <eblake <at> redhat.com>
To: Mark Wotton <mwotton <at> gmail.com>,
 Santiago Ruano Rincón <santiagorr <at> riseup.net>
Cc: 22071 <at> debbugs.gnu.org
Subject: Re: bug#22071: incorrect behaviour for inverted matches with -l on
 empty files
Date: Wed, 2 Dec 2015 06:32:11 -0700

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

On 12/02/2015 06:14 AM, Mark Wotton wrote:
> hm. "grep -l '' empty" also doesn't print anything, so I guess it's
> consistent, at least.

You want 'grep -L "hi there" ./empty', which says to print the names of
all files that did not contain any match (and not the names of all files
that had lines that didn't match).  That is, -v and -L are different
types of negation.

$ grep -L '' empty
empty
$ grep -Lv '' empty
empty

The empty file has no matches to any patterns (whether or not the
pattern is negated with -v), so it shows up under -L.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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Message #17 received at 22071 <at> debbugs.gnu.org (full text, mbox):

From: Mark Wotton <mwotton <at> gmail.com>
To: Eric Blake <eblake <at> redhat.com>
Cc: Santiago Ruano Rincón <santiagorr <at> riseup.net>,
 22071 <at> debbugs.gnu.org
Subject: Re: bug#22071: incorrect behaviour for inverted matches with -l on
 empty files
Date: Wed, 2 Dec 2015 08:57:49 -0500

Yes, I understand the interpretation now. Just confusing when you have
a model in mind that almost always works.

On 12/2/15, Eric Blake <eblake <at> redhat.com> wrote:
> On 12/02/2015 06:14 AM, Mark Wotton wrote:
>> hm. "grep -l '' empty" also doesn't print anything, so I guess it's
>> consistent, at least.
>
> You want 'grep -L "hi there" ./empty', which says to print the names of
> all files that did not contain any match (and not the names of all files
> that had lines that didn't match).  That is, -v and -L are different
> types of negation.
>
> $ grep -L '' empty
> empty
> $ grep -Lv '' empty
> empty
>
> The empty file has no matches to any patterns (whether or not the
> pattern is negated with -v), so it shows up under -L.
>
> --
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
>


-- 
A UNIX signature isn't a return address, it's the ASCII equivalent of a
black velvet clown painting. It's a rectangle of carets surrounding a
quote from a literary giant of weeniedom like Heinlein or Dr. Who.
        -- Chris Maeda

Message #22 received at 22071-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Mark Wotton <mwotton <at> gmail.com>
Cc: 22071-done <at> debbugs.gnu.org
Subject: Re: bug#22071: incorrect behaviour for inverted matches with -l on
 empty files
Date: Wed, 2 Dec 2015 08:11:20 -0800

On 12/02/2015 05:57 AM, Mark Wotton wrote:
> Yes, I understand the interpretation now.

Thanks, closing the bug.

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