GNU bug report logs - #24024
grep: Mixing "max-count" and "after-context" outputs too few lines

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

From: Santiago Ruano Rincón <santiagorr <at> riseup.net>
To: Igor Bogomazov <ygrex <at> ygrex.ru>, 831673 <at> bugs.debian.org,
 bug-grep <bug-grep <at> gnu.org>
Subject: grep: Mixing "max-count" and "after-context" outputs too few lines
Date: Tue, 19 Jul 2016 13:53:45 +0200

Hi,

Igor Bogomazov <ygrex <at> ygrex.ru> filed the following bug against grep in
Debian.

El 18/07/16 a las 14:30, Igor Bogomazov escribió:
> Package: grep
> Version: 2.25-6
> Severity: normal
> 
> 
> Given after-context=3 it is expected to output at least 4 lines
> as documented, but adding max-count=1 makes it stop on the next
> matching line.
> 
> What I do:
> 
> $ printf '%s\n' a b a c | grep -m1 -A3 a
> 
> What I see:
> 
> a
> b
> 
> What I expect:
> 
> a
> b
> a
> c
> 
> -- System Information:
> Debian Release: stretch/sid
>   APT prefers unstable
>   APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable')
> Architecture: amd64 (x86_64)
> 
> Kernel: Linux 4.6.0-1-amd64 (SMP w/4 CPU cores)
> Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
> Shell: /bin/sh linked to /bin/dash
> Init: systemd (via /run/systemd/system)
> 
> Versions of packages grep depends on:
> ii  dpkg          1.18.9
> ii  install-info  6.1.0.dfsg.1-8
> ii  libc6         2.23-1
> ii  libpcre3      2:8.38-3.1
> 
> grep recommends no packages.
> 
> Versions of packages grep suggests:
> ii  libpcre3  2:8.38-3.1
> 
> -- no debconf information
> 

Note also the behavior when there is not a second match:

% printf '%s\n' a b d c | grep -m1 -A3 a
a
b
d
c

Cheers,

Santiago

Message #8 received at 24024 <at> debbugs.gnu.org (full text, mbox):

From: Norihiro Tanaka <noritnk <at> kcn.ne.jp>
To: Santiago Ruano Rincon <santiagorr <at> riseup.net>
Cc: 24024 <at> debbugs.gnu.org, 831673 <at> bugs.debian.org, ygrex <at> ygrex.ru
Subject: Re: bug#24024: grep: Mixing "max-count" and "after-context" outputs
 too few lines
Date: Wed, 27 Jul 2016 00:38:02 +0900

> Igor Bogomazov <ygrex <at> ygrex.ru> filed the following bug against grep in
> Debian.
> 
> > $ printf '%s\n' a b a c | grep -m1 -A3 a
> > 
> > What I see:
> > 
> > a
> > b
> > 
> > What I expect:
> > 
> > a
> > b
> > a
> > c

As long as looking at prepending(), I see that it is designed but not
documented.

Message #13 received at 24024-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Santiago Ruano Rincón <santiagorr <at> riseup.net>
Cc: Norihiro Tanaka <noritnk <at> kcn.ne.jp>, 831673 <at> bugs.debian.org,
 24024-done <at> debbugs.gnu.org, ygrex <at> ygrex.ru
Subject: Re: bug#24024: grep: Mixing "max-count" and "after-context" outputs
 too few lines
Date: Wed, 7 Sep 2016 22:25:03 -0700

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

>> Given after-context=3 it is expected to output at least 4 lines
>> as documented, but adding max-count=1 makes it stop on the next
>> matching line.

Thanks for reporting this. Although grep's behavior is documented ("context does 
not include matching lines" in the node General Output Control) the 
documentation could be clearer and I installed the attached patch.

[0001-doc-define-context-lines.txt (text/plain, attachment)]

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