Bulk nslookup script

USAGE:

.\Resolve-IPs.ps1 -InputPath .\ips.txt -OutputPath .\resolved.csv

SCRIPT - 

param(

    [Parameter(Mandatory=$true)]

    [string]$InputPath,

    [Parameter(Mandatory=$true)]

    [string]$OutputPath

)

# Ensure input exists

if (-not (Test-Path -Path $InputPath)) {

    Write-Error "Input file not found: $InputPath"

    exit 1

}

# Create output directory if needed

$dir = Split-Path -Path $OutputPath -Parent

if ($dir -and -not (Test-Path $dir)) {

    New-Item -ItemType Directory -Path $dir | Out-Null

}

# Read IPs (ignore empty lines and lines starting with #)

$ips = Get-Content -Path $InputPath | ForEach-Object { $_.Trim() } | Where-Object { $_ -and ($_ -notmatch '^\s*#') }

# Prepare results

$results = @()

foreach ($ip in $ips) {

    $hostname = $null

    $status = "OK"

    try {

        # Reverse lookup

        $entry = [System.Net.Dns]::GetHostEntry($ip)

        $hostname = $entry.HostName

    }

    catch {

        $hostname = ""

        $status = "NXDOMAIN/No PTR or lookup failed"

    }

    $results += [PSCustomObject]@{

        IP       = $ip

        Hostname = $hostname

        Status   = $status

    }

}

# Export CSV

$results | Export-Csv -NoTypeInformation -Path $OutputPath -Encoding UTF8

Write-Host "Done. Results written to $OutputPath"