On 08/03/2017 06:28 AM, Santiago R.R. wrote:
the -o option, which is supposed to return only the matching
parts of the search, fails:
It's not failing. It's behaving as documented: -o outputs only nonempty
matches. Otherwise, commands like 'grep -o "a*"' would output a separate
line for each byte in the input. Although this behavior for -o is
longstanding and is documented in the manual, it's not in the grep
--help output so that's an oversight. I installed the attached to fix
grep --help, and am closing the bug report on the GNU side.
Users who want to match empty lines can use 'grep "^$"', which is what
I'd expect them to do anyway (-o would be superfluous there even if it
included empty matches).
>From fe06a81c1fdaeda10bfdde82b43e2b18bfd1de5e Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Thu, 3 Aug 2017 13:07:01 -0700
Subject: [PATCH] doc: improve -o help
* src/grep.c (usage): Document that -o outputs only nonempty
matches (Bug#27931).
---
src/grep.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/grep.c b/src/grep.c
index 8d22aec..dd338d9 100644
--- a/src/grep.c
+++ b/src/grep.c
@@ -1949,7 +1949,7 @@ Output control:\n\
--label=LABEL use LABEL as the standard input file name prefix\n\
"));
printf (_("\
- -o, --only-matching show only the part of a line matching PATTERN\n\
+ -o, --only-matching show only nonempty parts of lines matching PATTERN\n\
-q, --quiet, --silent suppress all normal output\n\
--binary-files=TYPE assume that binary files are TYPE;\n\
TYPE is 'binary', 'text', or 'without-match'\n\
--
2.13.3
