Powershell: list servers that respond

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#
# Create list of all servers with machine accounts in AD that respond to PING
#
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# Create $list of AD machine accounts for Windows Servers
$ServerList = ".\SERVERLIST.TXT"
New-Item $ServerList -Type file -Force >$nul
"Gathering Server List..."
$strCategory = "computer"
$strOS = "Windows*Server*"
$objDomain = New-Object System.DirectoryServices.DirectoryEntry
$objSearcher = New-Object System.DirectoryServices.DirectorySearcher
$objSearcher.SearchRoot = $objDomain
$objSearcher.Filter = ("OperatingSystem=$strOS")
$colProplist = "dnshostname"
foreach ($i in $colPropList){$objSearcher.PropertiesToLoad.Add($i)}
$colResults = $objSearcher.FindAll()
foreach ($objResult in $colResults) {
$objComputer = $objResult.Properties;
$Server = $objComputer.dnshostname
$Server = $Server -replace "\s{2,}", ""
$Server = $Server -replace "\.usa\.domain\.com", ""
if ($Server) {#skip null value
$Server
if (Test-Connection -ComputerName $Server -quiet -count 1) {#ping test
write-output $Server | out-file -encoding ASCII -filepath $ServerList -append
" .....OK"
}#if
}#if
}#foreach