Cross platform powershell to notify you when your dynamic IP changes

powershell_dynamic_ip_notifier.ps1

<#
Before you execute this, run this in powershell to get notification script installed:

Install-Module -Name PoshNotify
#>

$LOG="$HOME/.myip"

# Update the log file and show a notification with the current IP
function Update() {
    $ip_cur | Set-Content -NoNewline $LOG
    $hostname = hostname
    # Needs `Install-Module -Name PoshNotify`
    Send-OSNotification -Title "$($hostname) IP changed" -Body "Current IP: $ip_cur  Date: $(Get-Date -Format t)"
}

function InitLog() { 
    $ip_cur | Set-Content -NoNewline $LOG
}

while ($true) {
    # Check if the user has pressed Ctrl+C
    if ($Host.UI.RawUI.KeyAvailable) {
        $key = $Host.UI.RawUI.ReadKey("NoEcho, IncludeKeyDown")
        if ($key.VirtualKeyCode -eq 67 -and $key.Modifiers -eq "Control") {
            break
        }
    }

    $ip_response= Invoke-RestMethod -uri https://ipinfo.io/json | select-object -ExpandProperty ip
    $ip_cur= $ip_response.ToString()

    # If IP current is null exit, i.e. Invoke-WebRequest fails
    if (-not $ip_cur) {
        exit 1
    # If the log file doesn't exist
    } elseif (-not (Test-Path $LOG)) {
        InitLog
    } else {
        # Check if the IP has changed
        $ip_prev = Get-Content $LOG -First 1
        
        if ("$ip_prev" -ne "$ip_cur") {
            Update
        }
    }

    # Wait for one minute before checking again
    Start-Sleep -Seconds 60
}