Re: [PATCH/RFC] grep: optionally show only the match

["René Scharfe" <rene.scharfe@lsrfire.ath.cx>]

Am 09.09.2012 23:58, schrieb Marcus Karlsson:
> Make git-grep optionally omit the parts of the line before and after the
> match.
>
> Signed-off-by: Marcus Karlsson <mk@acc.umu.se>
> ---
>   Documentation/git-grep.txt | 8 +++++++-
>   builtin/grep.c             | 2 ++
>   grep.c                     | 7 +++++--
>   grep.h                     | 1 +
>   4 files changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
> index cfecf84..6ef22cb 100644
> --- a/Documentation/git-grep.txt
> +++ b/Documentation/git-grep.txt
> @@ -20,7 +20,8 @@ SYNOPSIS
>   	   [-c | --count] [--all-match] [-q | --quiet]
>   	   [--max-depth <depth>]
>   	   [--color[=<when>] | --no-color]
> -	   [--break] [--heading] [-p | --show-function]
> +	   [--break] [--heading] [-o | --only-matching]
> +	   [-p | --show-function]
>   	   [-A <post-context>] [-B <pre-context>] [-C <context>]
>   	   [-W | --function-context]
>   	   [-f <file>] [-e] <pattern>
> @@ -183,6 +184,11 @@ OPTIONS
>   	Show the filename above the matches in that file instead of
>   	at the start of each shown line.
>
> +-o::
> +--only-matching::
> +	Show only the part of the matching line that matched the
> +	pattern.
> +
>   -p::
>   --show-function::
>   	Show the preceding line that contains the function name of
> diff --git a/builtin/grep.c b/builtin/grep.c
> index 09ca4c9..56aba7b 100644
> --- a/builtin/grep.c
> +++ b/builtin/grep.c
> @@ -782,6 +782,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
>   			N_("print empty line between matches from different files")),
>   		OPT_BOOLEAN(0, "heading", &opt.heading,
>   			N_("show filename only once above matches from same file")),
> +		OPT_BOOLEAN('o', "only-matching", &opt.only_matching,
> +			N_("show only the matching part of a matched line")),
>   		OPT_GROUP(""),
>   		OPT_CALLBACK('C', "context", &opt, N_("n"),
>   			N_("show <n> context lines before and after matches"),
> diff --git a/grep.c b/grep.c
> index 04e3ec6..9fc888e 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -827,7 +827,9 @@ static void show_line(struct grep_opt *opt, char *bol, char *eol,
>   			if (match.rm_so == match.rm_eo)
>   				break;
>
> -			output_color(opt, bol, match.rm_so, line_color);
> +			if (opt->only_matching == 0)
> +				output_color(opt, bol, match.rm_so,
> +					     line_color);
>   			output_color(opt, bol + match.rm_so,
>   				     match.rm_eo - match.rm_so,
>   				     opt->color_match);
> @@ -837,7 +839,8 @@ static void show_line(struct grep_opt *opt, char *bol, char *eol,
>   		}
>   		*eol = ch;
>   	}
> -	output_color(opt, bol, rest, line_color);
> +	if (opt->only_matching == 0)
> +		output_color(opt, bol, rest, line_color);
>   	opt->output(opt, "\n", 1);
>   }

The implementation keeps only the coloured parts.  However, they are not 
necessarily the same as the matching parts.  This is more complicated 
with git grep than with regular grep because the former has the 
additional options --and and --not.  Consider this:

	$ git grep --not -e bla --or --not -e blub

Lines with only either "bla" or "blub" (or none of them) will be shown, 
lines with both not.  Both "bla" and "blub" will be highlighted.  The 
matching part is always the whole shown line.

René