Re: grab 'n' lines from a file above and below a /match/

[Anonymous Monk]

# In fat crayon mode for your pleasure
# spoofing your big log file handle as a little array for brevity
my @logs = ();
for(1..20){push(@logs, $_)}


my $lookBack    = 2;   # the number of lines behind the match you want
my $lookAhead   = 2;   # the number of lines ahead the match you want
my $matchReg    = '9'; # what your matching on (can be inlined)
my $matched     = 0;   # flag when we have a match
my @buffer      = ();  # your lookBack buffer

# Iterate through the logs looking for match
foreach my $line (@logs) {

   # Feed the buffer
   push(@buffer, $line);
   # Trim the buffer
   shift(@buffer) if $#buffer > ($lookBack-1);
   # Do stuff if this line matches
   if ($line =~ /$matchReg/) {

      # Print the buffer
      for(@buffer){print "lookback: $_\n"}
      # Wave a flag we have a match
      $matched = $lookAhead;
      # Nothing else to see here, move along
      next;
        
    }

    # Still working the lookAhead from a prior match?
    if($matched){

       # one less match
       --$matched;
       print "LookAhead: $line\n";

    }
}