Subject: Re: bug#24024: grep: Mixing "max-count" and "after-context" outputs too few lines

From: Paul Eggert <[email-masked]>
Date: Wed, 7 Sep 2016 22:25:03 -0700

>> 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.
From 90a2dd8b7f93ef0a8f08741e6fcb07220f9549f6 Mon Sep 17 00:00:00 2001
From: Paul Eggert <[email-masked]>
Date: Wed, 7 Sep 2016 22:22:37 -0700
Subject: [PATCH] doc: define "context lines"
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Reported by Igor Bogomazov via Santiago Ruano Rincón (Bug#24024).
* doc/grep.texi (Context Line Control): Define "context lines".
---
 doc/grep.texi | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/doc/grep.texi b/doc/grep.texi
index 80768dd..7e51d45 100644
--- a/doc/grep.texi
+++ b/doc/grep.texi
@@ -338,6 +338,7 @@ do
 done
 @end example
 
+@cindex context lines
 When @command{grep} stops after @var{num} matching lines,
 it outputs any trailing context lines.
 Since context does not include matching lines,
@@ -501,8 +502,11 @@ even those that contain newline characters.
 @node Context Line Control
 @subsection Context Line Control
 
+@cindex context lines
+@dfn{Context lines} are non-matching lines that are near a matching line.
+They are output only if one of the following options are used.
 Regardless of how these options are set,
-@command{grep} will never print any given line more than once.
+@command{grep} never outputs any given line more than once.
 If the @option{-o} (@option{--only-matching}) option is specified,
 these options have no effect and a warning is given upon their use.
 
@@ -530,7 +534,7 @@ Print @var{num} lines of leading context before matching lines.
 @opindex -C
 @opindex --context
 @opindex -@var{num}
-@cindex context
+@cindex context lines
 Print @var{num} lines of leading and trailing output context.
 
 @item --group-separator=@var{string}
-- 
2.7.4