Hi Monks,

I am trying to understand lastlogin.pl (a sample code from book Unix Programming - Programming Perl).
This sample code is working fine in my linux SuSe (after i changed $lastlog_t = "L a8 a256" to $lastlog_t="L a32 a256", and i know this after i did the super search at perlmonks and found this View last login times of everyone on your system).

So i have a conclusion that each record (fixed length records database) in /usr/var/lastlog has a "fixed" length, and the length of each record is 292 bytes 

$lastlog_t = "L a32 a256"; #(your machine maybe differ);
$LEN = length(pack($lastlog_t,0, '', ''));
print "length = $LEN \n";

[download]

Then, in my shell i did 'ls -l /var/log/lastlog', and i see that the size of lastlog is 146292 bytes.

So the sum of all records = 146292 / 292 = 501 records .

i am not sure about this, because when i ran lastlogin.pl there are only 16 UIDs.

i am curious, i used a sample script like this : 

setpwent();
while(@list = getpwent()) {
  ($login,$home) = @list[0,7];
  print "home directory for $login is $home \n";
}
endpwent();

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and still only display 16 records.

And now im confused, my /var/log/lastlog's size should be 4672 bytes not 146292 bytes !
or did i miss something ? (btw i am really new to this linux world)
Do you have any clues ?

You can see lastlogin.pl in Persib's scratchpad

Update : here's the lastlogin.pl 

#!/usr/bin/perl


$lastlog_t = "L a32 a256"; #(your machine maybe differ);

$LEN = length(pack($lastlog_t,0, '', ''));
open(LASTLOG,'/var/log/lastlog') || die "can't open lastlog file: $! \
+n";
open(PASSWD,'/etc/passwd') || die "can't open passwd file: $! \n";

@month=(Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec);

while($varrec = <PASSWD>) {
  ($login,$pass,$uid,$gid,$gcos) = split(/:/,$varrec);
  $fullname = $gcos;
#  $fullname = ~ s/^[^,]*--(.*)\(.*/$1/ || $fullname =~ s/,.*//;
#try to uncomment code line above, cuz i got weird result
  if ($fullname =~ /&/) { #u dont want to know
    $name = $login;
    substr($name,0,1) = ~ tr/a-z/A-Z/;
    $fullname = ~ s/&/$name/;
  }
  seek(LASTLOG,$uid * $LEN, 0);
  read(LASTLOG,$lastlog,$LEN);

  ($time,$line,$host) = unpack($lastlog_t,$lastlog);
  push(@records, "$time:$login:$uid:$fullname");
}

@records = sort numerically @records;

foreach $record(@records) {
  ($time,$login,$uid,$fullname) = split(/:/,$record);
  if ($time) {
    ($sec,$min,$hour,$mday,$mon,$year) = localtime($time);
    $year +=1900;
    $date = "$mday $month[$mon] $year";
  }
  else {
    $date = "never";
  }
  write;
}

sub numerically {$a <=> $b; }

format top =
  Uid    Login    Full Name            Last Login


.
format STDOUT =
@>>>>> @<<<<<< @<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< @||||||||||||
$uid   $login  $fullname               $date

[download]

thanks, and sorry for my english

In reply to Fixed length record and lastlog's size by Persib

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