powershell scripts for gpo - info users logons

#by alex
#powershell script for write logon info

$domainname = (Get-WmiObject Win32_ComputerSystem).Domain
$dirtowrite = "\\fileservername\log$"
$log = $dirtowrite + "\-worklog.log" 
$logfile = $dirtowrite + "\-worklog.log"

function log([string]$txt)
{
 add-content $LOGFILE $txt 
}

$clienthostinfo = ""

function mainproc()
{
#if terminal server role installed, get client name too
if((gwmi -namespace root\cimv2\terminalservices -class win32_terminalservicesetting).TerminalServerMode -eq 1){
  Import-Module PSTerminalServices
  $clienthostinfo = "from:"+(Get-TSSession -Filter {$_.Username -like [Environment]::Username} | Select-Object ClientName).ClientName}

 "Logon event at " + $(Get-Date -UFormat "%d-%m-%Y %T") + " for $env:Username on $env:Computername" + " $clienthostinfo" | Out-file -Append -FilePath $("$dirtowrite\$env:Computername-AT-$env:Username@$domainname.log")
}#endof mainproc

try{
 mainproc
 $retcode = 0}
catch{
   $ErrorMessage = $_.Exception.Message
   $invocation = $PSItem.InvocationInfo
   log("Exception detected!`nError message:$ErrorMessage")
   log("invocation:`n$invocation")
   $retcode = -1
}

return $retcode