In my job I quite often find myself with a whole bunch of host names that I need IP’s for. I found it quite repetitive to keep opening a command prompt and typing “nslookup hostname”, then copying and pasting it somewhere. So I started googling. I have never used Powershell before, so this was a good little project to learn a few things.
There’s a few good things to be found by googling for an introduction to powershell, so I won’t go over it here. The highlight is probably this article: Running Windows PowerShell Scripts which tells you how to actually run the scripts.
My scripts takes a text file as an input (which it opens a usual Windows “Open” dialog to let you choose), which needs to contain a list of hosts, one host per line. It will then perform a .NET DNS Lookup ([System.Net.Dns]::GetHostEntry), which is very similar to an nslookup but it returns an object which is more easily manipulated than the text based nslookup. It then outputs to a CSV file, with one line per entry containing all of the IP’s returned (in the case of multiple DNS entries).
The script is available here: bulk_dns_lookup on GitLab
Included in the file is the PowerShell script, which I will past in full on the next page. There is also a sample hostlist.txt file. And finally, a shortcut. The shortcut runs the script, bypassing the PowerShell execution policy settings. It is just a shortcut to: “C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -executionpolicy bypass -Sta -File script_dns_lookup.ps1”
I hope this is useful for someone! :o)
As promised, the code:
:::powershell
# *****************************************************************
# Bulk NSLOOKUP utility. Put a list of hosts in a text file, one
# per line, and run this file.
# Output will be in DNSLookup_Results.csv.
#
# Created by Nick Shaw
# Version 2. 25/11/13
# *****************************************************************
Function Get-FileName($initialDirectory)
{
[System.Reflection.Assembly]::LoadWithPartialName("System.windows.forms") |
Out-Null
$OpenFileDialog = New-Object System.Windows.Forms.OpenFileDialog
$OpenFileDialog.initialDirectory = $initialDirectory
$OpenFileDialog.filter = "All files (*.*)| *.*"
$OpenFileDialog.ShowDialog() | Out-Null
$OpenFileDialog.filename
}
#end function Get-FileName
$path = Get-FileName
if (-Not($path)) { exit }
$hosts = Get-Content $path
$totalhosts = $hosts.length
echo "Looking up DNS records for $totalhosts hosts...please be patient..."
$textresults = @()
$hostcounter = 1
foreach ($indivhost in $hosts)
{
echo "Looking up host $hostcounter of $totalhosts"
$hostcounter += 1
Try
{
$hostentry = [System.Net.Dns]::GetHostEntry($indivhost)
$singletextresult = """$($hostentry.hostname)"""
foreach ($address in $hostentry.addresslist)
{
$singletextresult += ",""$($address.IPAddressToString)"""
}
$textresults += $singletextresult
}
catch
{
$singletextresult = """$indivhost"",""Not Found"""
$textresults += $singletextresult
}
}
$savefilename = "DNSLookup_Results.csv"
$textresults | Out-File $savefilename -Encoding utf8
echo "DNS Lookups completed. Results are stored in $savefilename"
Write-Host "Press any key to continue ..."
$x = $host.UI.RawUI.ReadKey("NoEcho,IncludeKeyDown")
