[patch #7786] Support for multiple fixed multiline pattern matching

[Jiyong Jang]

URL:
  <http://savannah.gnu.org/patch/?7786>

                 Summary: Support for multiple fixed multiline pattern
matching
                 Project: grep
            Submitted by: jiyongj
            Submitted on: Mon 28 May 2012 06:28:37 PM GMT
                Category: None
                Priority: 5 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any

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Details:

Attached is a patch that adds a new option (-J) to support multiple fixed
multiline pattern matching. We couldn't figure out how to search a fixed
multiline pattern using grep, so we've added this option. Please let us know
if we're missing something. :) This was originally for our research project,
but we thought that this option might be also useful to others. 

One way to grep a multiline pattern is to use -z option like "grep -GHnz
<pattern> <file>" where <pattern> is "line1.line2.line3". Some small problems
with this method would be a) -n option becomes meaningless because it would
always return line #1, b) basic regex matching (-G option, default) would be
slower than fixed string matching (-F option), and c) it would print whole
file content instead of only matching lines if there's any match.

So, we've added a new option to extend grep's fast fixed string matching
method for multiline string search. Our patch is quite straightforward. 

*Usage:

$ ./grep -JHn "`echo -e "/* The color strings used for matched text.\n   The
user can overwrite them using the deprecated\n   environment variable
GREP_COLOR or the new GREP_COLORS."`" main.c

main.c:130:/* The color strings used for matched text.
   The user can overwrite them using the deprecated
   environment variable GREP_COLOR or the new GREP_COLORS.  */

Or for multiple fixed multiline strings,

$ ./grep -JHn -f multi.txt main.c

main.c:130:/* The color strings used for matched text.
   The user can overwrite them using the deprecated
   environment variable GREP_COLOR or the new GREP_COLORS.  */
static const char *selected_match_color = "01;31";      /* bold red */
static const char *context_match_color  = "01;31";      /* bold red */

main.c:136:/* Other colors.  Defaults look damn good.  */
static const char *filename_color = "35";       /* magenta */
static const char *line_num_color = "32";       /* green */
static const char *byte_num_color = "32";       /* green */
static const char *sep_color      = "36";       /* cyan */
static const char *selected_line_color = "";    /* default color pair */
static const char *context_line_color  = "";    /* default color pair */

where "multi.txt" has 
/* The color strings used for matched text.
   The user can overwrite them using the deprecated
   environment variable GREP_COLOR or the new GREP_COLORS.  */  
static const char *selected_match_color = "01;31";      /* bold red */
static const char *context_match_color  = "01;31";      /* bold red */
^@/* Other colors.  Defaults look damn good.  */  
static const char *filename_color = "35";       /* magenta */
static const char *line_num_color = "32";       /* green */
static const char *byte_num_color = "32";       /* green */
static const char *sep_color      = "36";       /* cyan */
static const char *selected_line_color = "";    /* default color pair */
static const char *context_line_color  = "";    /* default color pair */

^@ denotes NUL character for separating multiline patterns. In other words,
line 1-5 is the 1st multiline pattern that matches with main.c line #130, and
line 6-12 is the 2nd multiline pattern that matches with main.c line #136.

Best,
Jiyong Jang & Maverick Woo



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File Attachments:


-------------------------------------------------------
Date: Mon 28 May 2012 06:28:37 PM GMT  Name: grep-fixed-multiline.patch  Size:
5kB   By: jiyongj

<http://savannah.gnu.org/patch/download.php?file_id=25947>

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