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grep and display few lines before and after

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Operating Systems Solaris grep and display few lines before and after
# 1  
Old 12-07-2006
grep and display few lines before and after


is there a way in grep to display few lines before and after the pattern??

I tried options A and B and after-context and before-context. But they don't work on Solaris platform.

please advise.
# 2  
Old 12-07-2006
nawk 'c-->0;$0~s{if(b)for(c=b+1;c>1;c--)print r[(NR-c+1)%b];print;c=a}b{r[NR%b]=$0}' b=2 a=4 s="string" file1

...where "b" and "a" are the number of lines to print before and after string "s".


It's not the best generic solution because it can't handle the case if the search string is repeated in the "before" lines.

A better way...
nawk '$0~s{for(c=NR-b;c<=NR+a;c++)r[c]=1}{q[NR]=$0}END{for(c=1;c<=NR;c++)if(r[c])print q[c]}' b=2 a=4 s="string" file1

...where "b" and "a" are the number of lines to print before and after string "s".

Last edited by Ygor; 05-31-2012 at 08:51 AM.. Reason: Had to update this post because my buggy code is propagating all over the internet.
These 6 Users Gave Thanks to Ygor For This Post:
# 3  
Old 01-03-2007
little explanation required

Hi Ygor,

Could you explain this awk code. I am a bit confused with this.

# 4  
Old 01-03-2007
I do not know if it works on Solaris, I'm an AIX/Lnx. GNU grep has the feature '-A num' and '-B num' to display n rows before and/or after the pattern.
# 5  
Old 01-03-2007
Here you go..
I can't remember where I found this, but it works really well.
# - windowed grep utility
# Change Log
# 13/11/2006 - Goran Script Created

use strict;
use IO::File;
use IO::Handle;

my ($before,$after,$show_stars,$show_nums,$sep,$show_fname);
my ($show_sep,$arg,$file,$regexp,$lnum,$fhandle,$nbef,$naft);
my ($matched,$matched2,@line_buf,@temp,$fh,$ret);

$before = 3; $after = 3;         # default window size
$show_stars = 0;
$show_nums = 0;
$sep = "**********\n";
$show_fname = 1;
$show_sep = 1;

# loop until an argument doesn't begin with a "-"
while ($ARGV[0] =~ /^-(\w)(.*)/) {
   $arg = $1;                    # $arg holds the option letter
if ($arg eq "s") { $show_stars = 1; }
elsif ($arg eq "n") { $show_nums = 1; }
elsif ($arg eq "m") { $show_fname = 0; }
elsif ($arg eq "d") { $show_sep = 0; }
elsif ($arg eq "w") {
   # parse 2nd matched section at colon
   $before = $temp[0] if $temp[0] ne '';
   $after = $temp[1] if $temp[1] ne '';
elsif ($arg eq "p") {
   $before = 0;
   $after = 0;
   $show_sep = 0; }
elsif ($arg eq "W") {
   $before = 0;
   $after = 0;
elsif ($arg eq "h") { &usage(""); }
else { &usage("wgrep: invalid option: $ARGV[0]");
   }                             # end of if command
shift;                           # go on to next argument
}                                # end of foreach loop
&usage("wgrep: missing regular expression") if ! $ARGV[0];
$regexp = $ARGV[0];
$regexp =~ s,/,\\/,g;            # "/" --> "\/"

# if no files are specified, use standard input
if (! @ARGV[0]) { @ARGV[0] = "STDIN"; }

foreach $file (@ARGV) {          # loop over file list
   if ($file eq "STDIN") {
      $fh=new IO::Handle;
      die "Can't open STDIN." unless $ret;
   else {
      $fh = new IO::File "$file", "r";
      if (! defined $fh) {
         print STDERR "Can't open file $file; skipping it.\n";
         next LOOP;              # jump to LOOP label
$lnum = 0;
$nbef = 0; $naft = 0;
$matched = 0; $matched2 = 0;
&clear_buf(0) if $before > 0;
while (<$fh>) {                  # loop over the lines in the file
   ++$lnum;                      # increment line number
   if ($matched) {               # we're printing the match window
      if ($_ =~ /$regexp/) {     # if current line matches pattern:
         $naft = 0;              #   reset the after window count,
         &print_info(1);         #   print preliminary stuff,
         print $_;               #   and print the line
      else {                     # current line does not match
         if ($after > 0 && ++$naft <= $after) {
            # print line anyway if still in the after window
            &print_info(0); print $_;
         else {                  # after window is done
            $matched = 0;        # no longer in a match
            $naft = 0;           # reset the after window count
            # save line in before buffer for future matches
            push(@line_buf, $_); $nbef++;
            }                    # end else not in after window
         }                       # end else curr. line not a match
      }                          # end if we're in a match

   else {                        # we're still looking for a match
      if ($_ =~ /$regexp/) {     # we found one
         $matched = 1;           # so set match flag
         # print file and/or section separator(s)
         print $sep if $matched2 && $nbef > $before && $show_sep && $show_fname;
         print "********** $file **********\n" if ! $matched2++ && $show_fname;
         # print and clear out before buffer and reset before counter
         &clear_buf(1) if $before > 0; $nbef = 0;
         print $_;               # print current line
      elsif ($before > 0) {
         # pop off oldest line in before buffer & add current line
         shift(@line_buf) if $nbef >= $before;
         push(@line_buf,$_); $nbef++;
         }                       # end elseif before window is nonzero
      }                          # end else not in a match

   }                             # end while loop over lines in this file
}                                # end foreach loop over list of files
exit;                            # end of script proper

# subroutines #
sub print_info {
   print $_[0] ? "* " : "  " if $show_stars;
   printf "%4d ", $lnum if $show_nums;
}                                # end subroutine print_info

sub clear_buf {
   # argument says whether to print before window or not
   my ($i,$j,$print_flag);
   $print_flag = $_[0];
   $i = 0; $j = 0;
   if ($print_flag) {
      # if we're printing line numbers, fiddle with the
      # counter to account for the before window
      if ($show_nums) {
         $lnum -= ($#line_buf + 1);
      while ($j <= $#line_buf) { # print before window
         print $line_buf[$j++];
         $lnum++ if $show_nums;
         }                       # end while
      }                          # end if print_flag
   @line_buf = ();               # clear line_buf array
}                                # end subroutine clear_buf

sub usage {
   # optional argument is an additional message line
   print STDERR $_[0],"\n" if $_[0];
   print STDERR "Usage: wgrep [-n] [-w[B][:A] | -W] ";
   print STDERR "[-d] [-p] [-s] [-m] regexp file(s)\n";
   print STDERR "       -n = number lines\n";
   print STDERR "       -s = mark matched lines with asterisks\n";
   print STDERR "       -wB:A = display B lines before and A lines after\n";
   print STDERR "               each matched line [both default to 3]\n";
   print STDERR "       -W = suppress window; equivalent to -w0:0\n";
   print STDERR "       -d = suppress separation lines between sections\n";
   print STDERR "       -m = suppress file name header lines\n";
   print STDERR "       -p = plain mode: equivalent to -W -d\n";
   print STDERR "       -h = print this help message and exit\n";
   print STDERR "Note: If present, -h prevails; otherwise, the rightmost\n";
   print STDERR "      option wins in the case of contradictions.\n";

# 6  
Old 01-03-2007
Here's an example of how I have used wgrep on one of our Sunfire v440 servers
[tst1/] uname -a
SunOS tst1 5.9 Generic_112233-10 sun4u sparc SUNW,Sun-Fire-V440
[tst1/] prtpicl -v -c temperature-sensor | wgrep -w0:6 HighPowerOffThreshold | grep -v Low
********** STDIN **********
  :HighPowerOffThreshold         120 
  :HighShutdownThreshold         102 
  :HighWarningThreshold  97 
  :Temperature   43 
  :HighPowerOffThreshold         120 
  :HighShutdownThreshold         102 
  :HighWarningThreshold  97 
  :Temperature   45 
  :HighPowerOffThreshold         75 
  :HighShutdownThreshold         65 
  :HighWarningThreshold  60 
  :Temperature   25 
  :HighPowerOffThreshold         75 
  :HighShutdownThreshold         65 
  :HighWarningThreshold  60 
  :Temperature   25 
  :HighPowerOffThreshold         62 
  :HighShutdownThreshold         52 
  :HighWarningThreshold  47 
  :Temperature   21 
  :HighPowerOffThreshold         85 
  :HighShutdownThreshold         75 
  :HighWarningThreshold  65 
  :Temperature   27 

# 7  
Old 06-09-2008
Originally Posted by Ygor
nawk 'c-->0;$0~s{if(b)for(c=b+1;c>1;c--)print r[(NR-c+1)%b];print;c=a}b{r[NR%b]=$0}' b=2 a=4 s="string" file1

...where "b" and "a" are the number of lines to print before and after string "s".
This is exactly what I needed.
Thank you so much.
This User Gave Thanks to Primate For This Post:

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