Powershell script to check my external IP periodically

checkip.ps1

<#
.SYNOPSIS
    Checks and logs the external IP address at a specified interval.
.DESCRIPTION
    This script periodically fetches the public IP address from a specified web service
    and logs it to a file and the console. The check period, IP endpoint, and log file
    can be customized via parameters.
.PARAMETER PeriodSeconds
    The interval in seconds at which to check the IP address. Must be a positive integer.
    Default is 60 seconds.
.PARAMETER Endpoint
    The URL of the service to use for checking the IP address (e.g., "ifconfig.me", "ipinfo.io/ip").
    Default is "ifconfig.me".
.PARAMETER LogFile
    The path to the log file where IP address checks will be recorded.
    Default is "external_ip.log" in the script's directory.
.PARAMETER Help
    Displays this help message.
.EXAMPLE
    .\Get-ExternalIpPeriodically.ps1
    Runs with default settings: checks every 60 seconds using ifconfig.me, logs to external_ip.log.
.EXAMPLE
    .\Get-ExternalIpPeriodically.ps1 -PeriodSeconds 30
    Checks the IP every 30 seconds.
.EXAMPLE
    .\Get-ExternalIpPeriodically.ps1 -PeriodSeconds 120 -Endpoint "ipinfo.io/ip"
    Checks every 2 minutes using the ipinfo.io/ip service.
.EXAMPLE
    .\Get-ExternalIpPeriodically.ps1 -LogFile "C:\Logs\MyPublicIP.txt" -PeriodSeconds 300
    Checks every 5 minutes and logs to C:\Logs\MyPublicIP.txt.
.EXAMPLE
    .\Get-ExternalIpPeriodically.ps1 -Help
    Displays the help information.
.NOTES
    Author: Gemini
    Version: 1.0
    To stop the script, press Ctrl+C.
    Ensure your PowerShell execution policy allows running scripts.
    You might need to run: Set-ExecutionPolicy RemoteSigned -Scope CurrentUser
#>
[CmdletBinding()]
param(
    [Parameter(Mandatory=$false, HelpMessage="Check period in seconds (e.g., 30 for 30 seconds). Default: 60")]
    [ValidateRange(1, [int]::MaxValue)] # Ensures it's a positive integer
    [int]$PeriodSeconds = 60,

    [Parameter(Mandatory=$false, HelpMessage="IP check endpoint (e.g., 'ipinfo.io/ip', 'api.ipify.org'). Default: 'ifconfig.me'")]
    [string]$Endpoint = "ifconfig.me",

    [Parameter(Mandatory=$false, HelpMessage="Path to the log file. Default: 'external_ip.log' in script directory")]
    [string]$LogFile = (Join-Path $PSScriptRoot "external_ip.log"),

    [Parameter(Mandatory=$false, HelpMessage="Display this help message.")]
    [switch]$Help
)

# --- Function to display usage (using Get-Help) ---
if ($Help) {
    Get-Help $MyInvocation.MyCommand.Definition -Full
    exit 0
}

# --- Function to get the external IP address ---
function Get-ExternalIp {
    param(
        [string]$CurrentEndpoint,
        [string]$CurrentLogFile,
        [int]$CurrentPeriodSeconds
    )

    $Timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
    $ExternalIp = $null
    $LogMessage = ""

    try {
        # Add "http://" or "https://" if not present, common for simple endpoints like "ifconfig.me"
        $Uri = $CurrentEndpoint
        if (-not ($Uri.StartsWith("http://") -or $Uri.StartsWith("https://"))) {
            $Uri = "http://" + $Uri # Default to http, some services might require https
        }

        # Invoke-RestMethod is often better for APIs as it tries to parse the result
        # Using -UseBasicParsing to avoid issues with IE first launch configuration
        # Setting a timeout for the web request
        Write-Verbose "Attempting to fetch IP from $Uri"
        $ExternalIp = Invoke-RestMethod -Uri $Uri -TimeoutSec 10 -UseBasicParsing
    }
    catch {
        $ErrorMessage = $_.Exception.Message
        $LogMessage = "$Timestamp - Error: Could not retrieve IP from $CurrentEndpoint. Details: $ErrorMessage (Period: ${CurrentPeriodSeconds}s)"
        Write-Warning $LogMessage
        $LogMessage | Add-Content -Path $CurrentLogFile
        return # Exit function on error
    }

    if (-not [string]::IsNullOrWhiteSpace($ExternalIp)) {
        # Basic validation for an IP address format (can be improved for stricter IPv4/IPv6 checks)
        # This regex matches common IPv4 and IPv6 patterns.
        $IpPattern = '^((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4}$|^(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4}|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4})$'
        if ($ExternalIp -match $IpPattern) {
            $LogMessage = "$Timestamp - External IP: $ExternalIp (Endpoint: $CurrentEndpoint, Period: ${CurrentPeriodSeconds}s)"
            Write-Host $LogMessage -ForegroundColor Green
        } else {
            $LogMessage = "$Timestamp - Warning: Received non-IP response from $CurrentEndpoint: '$ExternalIp' (Period: ${CurrentPeriodSeconds}s)"
            Write-Warning $LogMessage
        }
    } else {
        $LogMessage = "$Timestamp - Warning: Received empty response from $CurrentEndpoint. (Period: ${CurrentPeriodSeconds}s)"
        Write-Warning $LogMessage
    }

    # Log to file
    if (-not [string]::IsNullOrWhiteSpace($LogMessage)) {
        try {
            $LogMessage | Add-Content -Path $CurrentLogFile -ErrorAction Stop
        }
        catch {
            Write-Error "Failed to write to log file $CurrentLogFile. Error: $($_.Exception.Message)"
        }
    }
}

# --- Main loop ---
Write-Host "Starting IP check..." -ForegroundColor Cyan
Write-Host "Check Period: $($PeriodSeconds) seconds" -ForegroundColor Cyan
Write-Host "IP Endpoint: $Endpoint" -ForegroundColor Cyan
Write-Host "Log File: $LogFile" -ForegroundColor Cyan
Write-Host "Press Ctrl+C to stop." -ForegroundColor Yellow

# Create log file directory if it doesn't exist
$LogDirectory = Split-Path -Path $LogFile -Parent
if (-not (Test-Path $LogDirectory)) {
    try {
        New-Item -ItemType Directory -Path $LogDirectory -Force -ErrorAction Stop | Out-Null
        Write-Verbose "Created log directory: $LogDirectory"
    }
    catch {
        Write-Error "Could not create log directory: $LogDirectory. Error: $($_.Exception.Message)"
        Write-Error "Please create the directory manually or choose a different log file path."
        exit 1
    }
}


# Trap Ctrl+C for graceful exit
trap {
    Write-Host "Script interrupted. Exiting." -ForegroundColor Yellow
    break # Breaks out of the loop
}

while ($true) {
    Get-ExternalIp -CurrentEndpoint $Endpoint -CurrentLogFile $LogFile -CurrentPeriodSeconds $PeriodSeconds
    Start-Sleep -Seconds $PeriodSeconds
}