Hi Parv,
Wish I could pay you! Sorry about your employment status! :-( Here is the Perl script that I created. This works for me and produces the output that I targetted for.

To start processing records by the quarter of the hour, for example, 14:00:00, 14:15,..., I checked for (($minute%15) !=0), right at the beginning of the subroutine count_recs.

#!/usr/bin/perl -w

use strict;

use Getopt::Long;
use Time::Local;
use Time::localtime;

my $file="xaa";
my %increment = ();
my $interval = 900;  #An interval of 15 minutes
my %MonthToNumber = ();
   @MonthToNumber{qw (Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec)
+} = map { sprintf "%02d", $_; } (0..11);

count_recs();

sub count_recs {
   my ($Day, $Month, $Year, $Hour, $Minute, $Second);
   my ($datetime, $get_post);
   my $dmytime;
   my $dateproc;
   my @dates = ();
   my @dates_mod = ();

   open (INFILE, "<$file") || die "Cannot read from $file";
   while (<INFILE>) {
      ($datetime,$get_post) = (split / /) [3,6]; 
      $datetime =~ s/\[//;
      ($Day,$Month,$Year,$Hour,$Minute,$Second)= $datetime =~m#^(\d\d)
+/(\w\w\w)/(\d\d\d\d):(\d\d):(\d\d):(\d\d)#;

      next 
         if ($get_post =~ /\.js$/ || $get_post =~ /\.gif$/ || $get_pos
+t =~ /\.css$/ || ($Minute%15) != 00);

         push (@dates, $datetime);
                         
   } #outer while

# Calculate the time in epoch seconds in the subroutine convert_epoch.
+ 

   foreach  $dmytime (@dates){
      my $calc_seconds= &convert_epoch($dmytime);
      push (@dates_mod, $calc_seconds); 
   }
   foreach $dateproc (@dates_mod) {
         $increment{$dateproc}++;
   }
# Print the headings in the output file
   open (OUTFILE, ">>access_log.out") || die "Cannot write to $file";
   print OUTFILE "     Date      Range of Time   Visual Pages per seco
+nd(VPPS)\n";
   print OUTFILE "                               Avg  Max Min\n";
   print OUTFILE "------------ ----------------- ------------\n"; 

   &calculate_time();
   print OUTFILE "\n\n\n";
  
   $interval = 3600;
   &calculate_time();
       
   close(OUTFILE);
   close(INFILE);
}

sub convert_epoch {
   my $localdate = shift;
   my ($epoch_Day,$epoch_Month,$epoch_Year,$epoch_Hour,$epoch_Minute,$
+epoch_Second)= $localdate =~m#^(\d\d)/(\w\w\w)/(\d\d\d\d):(\d\d):(\d\
+d):(\d\d)#;
   my $epoch_seconds = timelocal($epoch_Second, $epoch_Minute, $epoch_
+Hour, $epoch_Day, $MonthToNumber{$epoch_Month}, $epoch_Year-1900);
   return $epoch_seconds;
}

sub calculate_time {
   my $first = 0;
   my $start_time;
   my $end_time;
   my $time;
   my ($max, $min, $avg, $count);
   my $partial=0;
   my $col_ind;
   my $processed; 
   my $tm;
   foreach $processed ( sort keys %increment ) {
      if ($first == 0 ) {
          $start_time = $processed;
          $end_time   = $start_time + $interval;
          $time = $start_time;
          $min = $increment{$processed};
          $max = 0;
          $avg = 0;
         $first++;                 
      }
      if ($processed < $end_time) {
         if ($increment{$processed} < $min) {
             $min = $increment{$processed}; 
         }        
         if ($increment{$processed} > $max) {
             $max = $increment{$processed}; 
         }
         $avg+= $increment{$processed};
         $count++; 
         $partial = 1;
      }else {
          $avg=$avg/$count; 
          my $tm = localtime($end_time);
          my $start = localtime($start_time);
          if ($interval == 900) {
             $col_ind = 'P';
          }else {
              $col_ind = 'H'; 
          }
          printf OUTFILE "%01s %02d/%02d/%04d %02d:%02d:00-%02d:%02d:0
+0 %03.2f %03d %03d\n", $col_ind, ($tm->mon)+1,$tm->mday, $tm->year+19
+00,$start->hour, $start->min, $tm->hour,$tm->min, $avg, $max, $min;
          $min = $increment{$processed};
          $max = $increment{$processed};
          $avg = $increment{$processed};     
          $count = 1;
          $start_time = $processed;
          $time = $start_time;
          $end_time   = $start_time + $interval;
          $partial  = 0;
      }
   }
   if ( $partial == 1 ) {
      $avg = $avg/$count;
      $tm = localtime($end_time);
      my $start = localtime($start_time);
      printf OUTFILE "%01s %02d/%02d/%04d %02d:%02d:00-%02d:%02d:00 %0
+3.2f %03d %03d\n", $col_ind, ($tm->mon)+1,$tm->mday, $tm->year+1900,$
+start->hour, $start->min, $tm->hour,$tm->min, $avg, $max, $min;
   }
}
[download]

Pl. suggest any improvements you can think of. I know that I used the MonthToNumber (convert "Apr" to "04" and so on) as a Global. Thanks to you for that input.

Also, I used the hash %increment as a global. May be I could pass it as an argument to the subroutine calculate_time?

I needed to process two intervals of time, 15min and 1 hour. That's why I called the subroutine twice, with the interval used globally. Any thoughts?

Performance wise, I got a 100MB file processed in about 1min 5 secs.

My next step is to be able to process multiple input files. Currently, I hardcoded an input file. But, I would like to pass multiple log files as input and process them all.
-Andy

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