Hello,

I've got some huge apache log files which I want to search backwards for the last access to a particular url. I can do this from the command line very effectively with this:

tac reall_big_access_log | grep -m 1 "/myapp/"

It's really fast, which is what I like about it. The -m 1 part of the grep command kills tac upon finding the first match, so file reading is minimized.

I've tried several ways of writing a script to interate over these access logs and execute the same statement, but I've had no luck. Each method I've tried that involved system() resulted in the tac command not being killed by the grep -m 1 statement, so the tac commands crawl through the entirety of every log file, which takes a very long time.

Below is my current script, which relies on File::ReadBackwards to emulate tac. This is quite a bit slower than the command line method as well. Could anyone suggest a good way to just execute the command line above inside a script?

Thank You,
Troy 

#!/usr/bin/perl
use strict;
use Date::Parse;
use File::ReadBackwards;

my $log_dir = '/var/log/httpd/';
my $session_limit = 3600; # 1 hour

my ($sec,$min,$hour,$mday,$month,$year,$wday,$yday,$isdst) = localtime
+(time);
$year += 1900;
$month++;
my $date_cmp_str = join('', ($year, sprintf('%02d', $month), sprintf('
+%02d', $mday), $hour, $min, $sec));

print 'myapp user status' . "\n";
my @expired;
my @active;

opendir(DIR, $log_dir);
my @files = grep { /_access_log$/ } readdir(DIR);
closedir DIR;

print STDERR "Files = " . join(", ", @files) . "\n\n";

sleep(3);

foreach my $lf (@files) {
        my ($domain, $t1, $t2) = split("_", $lf);
        my $myapp_dir = '/w3/' . $domain . '/myapp/';
        if (!-e $myapp_dir) {
                next;
        }
        else {
                # Find last login
                my $file = $log_dir . $lf;
                my $last_line = '';
                my $bw = File::ReadBackwards->new($file) or die "can't
+ read '$file' $!";
                my $found = 0;
                while( !$found && defined( my $log_line = $bw->readlin
+e ) ) {
                        if ($log_line =~ /GET \/myapp\//) {
                                $last_line = $log_line;
                                $bw->close();
                        }
                }

                if ($last_line eq '') {
                        print "No access in logs.\n";
                }
                else {
                        my ($ip, $d1, $d2, $date, $tz, $method, $url, 
+$rest) = split(" ", $last_line);
                        $date = substr($date, 1);
                        $tz = substr($tz, 0, -1);
                        my $cdate = $date . ' ' . $tz;
                        my ($ss,$mm,$hh,$dy,$mon,$yr,$zone) = strptime
+($cdate);
                        $yr += 1900;
                        $mon++;
                        my $date_str = join('', ($yr, sprintf('%02d', 
+$mon), sprintf('%02d', $dy), $hh, $mm, $ss));
                        # print "Last myapp hit on $lf to $url by $ip 
+on $date_str \n";
                        #print "$mon/$dy/$yr $hh:$mm:$ss > $month/$mda
+y/$year $hour:$min:$sec ?\n";
                        my ($domain, $t3, $t4) = split("_", $lf);

                        if ($date_str > ($date_cmp_str - $session_limi
+t)) {
                                print "User logged in! $domain last hi
+t $mon/$dy/$yr $hh:$mm:$ss by IP $ip\n";
                        }
                        else {
                                print "$domain last hit $mon/$dy/$yr $
+hh:$mm:$ss by IP $ip\n";
                        }
                }
        }
}

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In reply to Emulating command line pipe by davistv

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