#!/usr/bin/perl

use User::Utmp qw(utmpname getut putut);

use constant LOGIN_PROCESS => 6;
use constant USER_PROCESS  => 7;
use constant DEAD_PROCESS  => 8;

my $debug = 0;
my ($start,$end,$utmp) = @ARGV;
utmpname($utmp || "/etc/wtmp");
@utmp = getut();

foreach $utmp (@utmp)
{ my ($user,$line,$type,$time)
   = @$utmp{'ut_user','ut_line','ut_type','ut_time'};

  next if $type < USER_PROCESS;  # we just care about logins and logouts
  next unless $line;  # entries for user logins never have a blank line
  next unless $user =~ /\w/; # skip pseudo-logins with no username

  my ($sec,$min,$hour,$mday,$mon,$year) = localtime($time);
  my $date = sprintf("%04d-%02d-%02d", $year+1900, $mon+1, $mday);
  my $hour = sprintf("%02d:%02d:%02d", $hour, $min, $sec);

  next if $start && $date lt $start;
  next if $end && $date gt $end;

  printf "user: %8s line: %12s type: %s time: %s %s\n",
    $user, $line, $type, $date, $hour
    if $debug;

  if ($type == USER_PROCESS)
  { $logins++;            # total logins for all users
    $logins{$user}++;     # total number of times this user logged on
    ++$multlogins && ++$multlogins{$user} if $loggedin{$user};
    $loggedin{$user}++;   # number of "current" logins at this point
    $user{$line} = $user; # which user is on this line?
  }
  elsif ($type == DEAD_PROCESS)
  { next unless $user{$line} eq $user;
    $loggedin{$user}--;
    delete $user{$line};
  }
}

print "\nSummary of logins";
print " after $start" if $start;
print " before $end" if $end;
print "\n";

@users = keys %logins;
$users = @users;
$avglogins = sprintf "%.2d", ($logins/$users);

foreach $user (@users)
{ printf "%8s logged in %6d times (%d multiple)\n",
    $user, $logins{$user}, $multlogins{$user};
}

print <<SUMMARY;

$logins logins
$multlogins multiple logins
$users different users logged in
average $avglogins logins/user

SUMMARY