#!/bin/perl
use File::Tail;

my $serverlog  = '/home/pat/minecraft/server.log';
my $outputhtml = '/home/pat/minecraft/online_users.html';

my %online = ();
my $ft = File::Tail->new(
   name => $serverlog,
   interval    => 5,
   maxinterval => 20,
   adjustafter => 15,
);

while (defined($line = $ft->read)) {
   if ($line =~ /INFO\]\s*(\w+)\s*.*logged in/) {
      $online{$1} = 1;
      print "[$1] online\n";
      update_status_file();
   } elsif ($line =~ /INFO\]\s*(\w+)\s*.*lost connection/) {
      $online{$1} = 0;
      print "[$1] offline\n";
      update_status_file();
   }
}

sub update_status_file {
   open my $out, '>', $outputhtml;
   print $out "Online:\n<ul>";
   for my $user (sort keys %online) {
      print $out "  <li>$user</li>" if $online{$user};
   }
   print $out "</ul>\n";
   close $out;
}