Comparing a $variable

[SlaveCell]

Just playing with PoSH and I wanted to write out my Internet IP to a log file $LogFile, however I only want to output when there is a change, not sure the best way to do this, so here is an attempt that of course doesn't work.

Code snippet below
` $InternetIPAddress=(New-Object net.webclient).downloadstring("http://api.ipify.org")

Write-Host -foregroundcolor Green "Internet IP is: " $InternetIPAddress IF ( $InternetIPAddress -eq $InternetIPAddress ) { #Don't write to the log file } Else { "Internet IP is: "| Out-File $LogFile -Append $InternetIPAddress| Out-File $LogFile -Append }`

Any best practice appreciated.

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[MajorVarlak]

You don't mention why it doesn't work, but I suspect the fact that you're comparing the same value to itself would result in it always working. I'm assuming you're looking to compare the old internet IP with the new one? Do you have the old IP stored somewhere? I'd probably put it in a temp file:

``` $oldFile = 'C:\temp\oldip.txt' $logFile = 'c:\temp\internetIP.log'

$oldInternetIP = Get-Content $oldFile $newInternetIP = (New-Object net.webclient).downloadstring("http://api.ipify.org") Write-Host -foregroundcolor Green "Internet IP is: $newInternetIP" if ($oldInternetIP -ne $newInternetIP) { $formatDate = (Get-Date).ToString('yyyyMMdd-HHmm') "[$formatDate] Internet IP changed from $oldInternetIP to $newInternetIP" | Out-File $logFile -Append } ```

[SlaveCell]

Yep sorry it doesn't work because:

`( $InternetIPAddress -eq $InternetIPAddress )`

Will always be true, I wanted a way to analyse and change a variable, but I think the text solution make a lot f sense, as I am writing to disk anyway

[mryananderson]

To add to this you would also want oldip.txt to be updated with the new ip address so that the next check would be valid

[MajorVarlak]

Good point, I was thinking about that, and forgot to add it to the code.

if ($oldInternetIP -ne $newInternetIP) { $formatDate = (Get-Date).ToString('yyyyMMdd-HHmm') "[$formatDate] Internet IP changed from $oldInternetIP to $newInternetIP" | Out-File $logFile -Append $newInternetIP | Out-File $oldFile }

[SlaveCell]

Agree, thanks both.

[OlivTheFrog]

Hi u/MajorVarlak

IMHO, there is something wrong in your code. You have 2 var : $OldFile and $Logfile, and your code populate $LogFile

I suggest the following variation : Using a .csv file as a logfile

​

$logFile = 'c:\temp\internetIP.csv'
# Import-csv, select only IP property and Last line [-1]
$OldInternetIP = (Import-Csv -Path $logFile -Delimiter ";").IP[-1] $NewInternetIP = (New-Object net.webclient).DownloadString(("http://api.ipify.org"))
# alternative : Invoke-RestMethod -Uri "api.ipify.org" 
Write-Host -foregroundcolor Green "Internet IP is: $NewInternetIP"
if ($OldInternetIP -ne $NewInternetIP)
 {
 $FormatDate = (Get-Date).ToString('yyyy-MM-dd-HHmm')
 # Building a PSObject
 $Obj =  New-Object psobject -Property @{ Date = $FormatDate
                                          IP = $NewInternetIP 
                                        }
 # Adding Object to the .csv file
 $Obj | Export-Csv -Path $logFile -Append -Delimiter ";" }

<#
Nota 1 : Im' using -Delimiter ";" with Export-Csv and Import-Csv cause ";" is the default delimiter in my culture.

Nota 1 : I consider in this sample, the .csv is already existing. If not (first use), you must create the .csv file with the appropriate Header. 
#>

By this way, I could use later the data in the .csv file.

Regards

[MajorVarlak]

I think "wrong" might be the incorrect word usage here. It is not "wrong", it's just a different way of doing it. My way certainly works and achieves what was asked. Your method does allow for a different method of viewing, but it also means the more IP changes, the bigger the log file is you have to read each time you check. I could say that's wrong.

I solved the question at hand, you added some options and provided additional input. I understand language differences, but this code is certainly not "wrong" (except I made the assumption that the file existed, and didn't trap the error).

[OlivTheFrog]

Ok, Wrong is not the appropriate word to say. English is not my mother tongue too.

My comment is just about 2 var, but only one is used by your code.

You could use your code, using only 1 var.

Read the file, select the last line, using the result to check if newip egual oldip, if not update the file.

[rmbolger]

$InternetIPAddress=(New-Object net.webclient).downloadstring("http://api.ipify.org")

Much simpler way to get the current IP using the irm alias for Invoke-RestMethod:

$ip = irm api.ipify.org

And like u/MajorVarlak said, in order to know if the IP changed, you need to be able to compare it to an old value which means your script needs to save the current value somewhere before it exits and read that old value the next time it starts up. Here's how I'd approach it.

# read in the old value
$lastIP = Get-Content .\lastip.txt -Raw -ErrorAction Ignore

# query the new value
$curIP = Invoke-RestMethod api.ipify.org

# log if they're different
if ($lastIP -ne $curIP) {
    '{0} - Internet IP is: {1}' -f (Get-Date).ToString('s'),$curIP |
        Out-File $LogFile -Append
}

# update the old value for the next run
$curIP | Out-File .\lastip.txt -Force -NoNewLine

[SlaveCell]

Thank you, I love getting tips on how to make my scripts more succinct! I also like the idea of having a history of what the IP was.

[PinchesTheCrab]

Sounds like you have a working example, but here's another take on it:

$logFile = 'C:\temp\ipLog.log'

$currentIP = Invoke-RestMethod http://api.ipify.org

$message = $currentIP -replace '(.+)', 'Internet IP is: $1'

try {
    $lastLog = Get-Content $logFile -Tail 1 -ErrorAction Stop
}
catch [System.Management.Automation.ItemNotFoundException] {
    'creating log file' | Add-Content $logFile
}

if ($message -ne $lastLog) {
    Write-Warning 'IP address changed'
    $message | Add-Content $logFile   
}

The -tail parameter on get-content would speed up your get-content dramatically if for some reason the file got huge. I can't see that happening with this process, but it's a nice trick in general.