#!/usr/bin/perl
# weekearly -- set someone's login date back a week
use User::pwent;
use IO::Seekable;

$typedef = 'L A12 A16';         # linux fmt; sunos is "L A8 A16"
$sizeof  = length(pack($typedef, ()));
$user    = shift(@ARGV) || $ENV{USER} || $ENV{LOGNAME};

$address = getpwnam($user)->uid * $sizeof;

open (LASTLOG, "+</var/log/lastlog")
    or die "can't update /usr/adm/lastlog: $!";
seek(LASTLOG, $address, SEEK_SET)
    or die "seek failed: $!";
read(LASTLOG, $buffer, $sizeof) == $sizeof
    or die "read failed: $!";

($time, $line, $host) = unpack($typedef, $buffer);
$time  -= 24 * 7 * 60 * 60;         # back-date a week
$buffer = pack($typedef, $time, $line, $time);

seek(LASTLOG, -$sizeof, SEEK_CUR)   # backup one record
    or die "seek failed: $!";
print LASTLOG $record;
    
close(LASTLOG)
    or die "close failed: $!";