How to get current logged on user

Import-Module ActiveDirectory
 
[System.Security.Principal.WindowsIdentity]::GetCurrent().Name
{
$dcs = Get-ADDomainController -Filter {Name -like "*"}
$users = Get-ADUser -LDAPFilter "(&(objectCategory=person)(objectClass=user))"
$time = 0
$exportFilePath = "c:\scripts\lastLogon.csv"
$columns = "name,username,datetime"
Out-File -filepath $exportFilePath -force -InputObject $columns
foreach($user in $users)
{
foreach($dc in $dcs)
{ 
$hostname = $dc.HostName
$currentUser = Get-ADUser $user.SamAccountName | Get-ADObject -Server $hostname -Properties lastLogon
if($currentUser.LastLogon -gt $time) 
{
$time = $currentUser.LastLogon
}
}
if($time -eq 0){
$row = $user.Name+","+$user.SamAccountName+",Never"
}
else {
$dt = [DateTime]::FromFileTime($time)
$row = $user.Name+","+$user.SamAccountName+","+$dt
}
Out-File -filepath $exportFilePath -append -noclobber -InputObject $row
$time = 0
}
}