Test-Hostname.ps1

# Monitor hostname ip change
# First create CSV
# Resolve-Host -HostName HostName | Export-Csv -Path $hosts_csv_path -Encoding UTF8
# or Add hosts
# Resolve-Host -HostName AnotherHostname | Export-Csv -Path $hosts_csv_path -Encoding UTF8 -Append

function Resolve-Host {
    param($HostName)
    BEGIN {
        Write-verbose "In function Resolve-Host"
    }
    PROCESS {
        Write-Verbose "$hostName"
        $host_ips = [System.Net.Dns]::GetHostAddresses("$hostName")
        if ($?) {
            foreach ($host_ip in $host_ips) {
                Write-Verbose "    $($host_ip.ipaddresstostring)"
                [pscustomobject][ordered]@{
                    HostName = $hostName
                    IP       = $host_ip.ipaddresstostring
                    Date     = Get-Date -Format ("yyyy-MM-dd")
                }			
            }
        }
    }
}

$OldVerbosePreference = $VerbosePreference
$VerbosePreference = "continue"

#path to csv with hosts and ips
$hosts_csv_path = "C:\Temp\hosts.csv"

$scriptname = $MyInvocation.MyCommand.Name
$LogPath = "c:\Logs\"
$log = "$LogPath$scriptname.log"
Start-Transcript $log

$email_props = @{
    SMTP    = "192.168.1.1"
    From    = "$env:[email protected]"
    To      = "[email protected]"   
}

if ($my_error) {
    Remove-Variable my_error -ErrorAction SilentlyContinue
}

Write-Verbose "CSV Path $hosts_csv_path"
try {
    $hosts_csv = Import-Csv $hosts_csv_path -ErrorVariable +my_error
} catch {
    Throw "Error importing $hosts_csv_path`nHint: Create CSV`n    Resolve-Host -HostName HostName | Export-Csv -Path $hosts_csv_path -Encoding UTF8`n$($my_error[0] | out-string)"
}
if (-not $hosts_csv.hostname -or $hosts_csv.count -eq 0) {
    Throw "No results from CSV file"
}
write-verbose "Hosts from file`n $($hosts_csv | out-string)"
#group by hostname
$host_list = $hosts_csv | Group-Object -Property hostname -ErrorVariable +my_error

$results = foreach ($host_single in $host_list) {
    $hostname = $host_single.Name
    $query = Resolve-Host -HostName $hostname
    if ($query) {
        foreach ($row in $query) {
            if (!($host_single.group.ip -contains $row.ip)) {
                $row
                Write-Verbose "    Add $($row.ip)"
            } else {
                Write-Verbose "    Skip $($row.ip)"
            }
        }
    }
}
if ($results) {
    Write-Verbose "Send mail with results"
    Send-MailMessage @email_props  -Subject "Hostname IP change" -Body $(($results | ForEach-Object {"$($_.ip) $($_.hostname)"}) -join "`n")
    Write-Verbose "Export results"
    $results | Export-Csv -Append $hosts_csv_path -NoTypeInformation -Encoding utf8 -ErrorVariable +my_error
}
Stop-Transcript

if ($my_error) {
    Write-Warning "Send Errors"
    Send-MailMessage @email_props -Subject "Error in $scriptname " -Body $(Get-Content $log)
}

$VerbosePreference = $OldVerbosePreference