Logging off from all servers in a domain

I notice a few things...

"First, I don't think quser | Where-Object {$_ -match $env:USERNAME} will ever return anything. The output of quser will not contain the hostname."

Try this for getting logon sessions:

$Sessions = (query user /server:$Env:ComputerName) -split "\n" -replace '\s\s+', ';' | 
    ConvertFrom-Csv -Delimiter ';'

Next, when you reference the $Server variable on the remote machine in your script block, it is out of scope. You would need to use $Using:Server in the script block.

Lastly, the -isnot operator doesn't compare value, it compares type. So in your last foreach, the if statement evaluates to "if type string is not type string" and will not run. Try -ne or -notlike instead.

So I modified the script this way and it works, sort of. It logs off account from servers, which is the main goal. There are still some glitches, like the message it sends from the first Write-Host doesn't give server's name, the message from second one gives a different value than it should (it gives [1] value after -split instead of [2] for some reason; but those are not really that important things, even though I will try to make at least the first message right) and $SessionIDs still gives only the first value, but usually you shouldn't have more than one RDP session per server. I've seen more sessions of one user, but that is very rare. But I'd also like to fix this if possible. Nevertheless, the script basically does the most important thing. But if someone has a suggestion how to fix the glitches I mentioned I would be grateful.

$ErrorActionPreference = "Silentlycontinue"
$Servers = (Get-ADComputer -Filter *).Name
$ScriptBlock = {
        $Sessions = quser | ?{$_ -match $env:USERNAME}
        if (($Sessions).Count -ge 1)
        {
            $SessionIDs = , ($Sessions -split ' +')[2]
            Write-Host "Found $(($SessionIDs).Count) user login(s) on $Server."
            Foreach ($SessionID in $SessionIDs)
            {
                Write-Host "Logging off session $SessionID..."
                logoff $SessionID
            }
        }
}
foreach ($Server in $Servers)
{
    if ($Server -ne $env:COMPUTERNAME)
    {
        Invoke-Command -ComputerName $Server -ScriptBlock $ScriptBlock
    }
}

Working with objects is much easier if you can just parse the output of QUser.exe. Given your scenario, here's my take on it:

$servers = (Get-ADComputer -Filter '*').Name.Where{$_ -ne $env:COMPUTERNAME}
foreach ($server in $servers)
{
    if (-not ($quser = ((QUser.exe /server:$server) -replace '\s{20,39}',',,' -replace '\s{2,}',',' 2>&1) | Where-Object -FilterScript { $_ -match $env:USERNAME })) {
        Continue
    }
    Write-Verbose -Message "$($quser.Count) session(s) found on $server." -Verbose
    ($quser.Trim() | ConvertFrom-Csv -Header 'USERNAME','SESSIONNAME','ID','STATE','IDLE TIME','LOGON TIME').foreach{
        Write-Verbose -Message "Logging user [$($_.UserName)] off." -Verbose
        LogOff.exe $_.ID /server:$server
    }
}

Filtering should always happen before hand meaning, filter out your computer name on your first call to Get-ADComputer. Since you're using QUser.exe and LogOff.exe to begin with, I'd recommend the use of it all the way through since LogOff accepts an ID value that QUser outputs.

Next, placing the call to quser inside your if statement does two things in this case.

1. Filters for all users matching $ENV:UserName
2. Returns $true if anything is found, and $false if not found.
   • So, switching the results using -not will turn $false into $true allowing the execution of the code block which will just continue to the next server.
   • This in turn doesn't bother with the rest of the code and continues onto the next computer if no matching names were found.

The use of $quser inside the if statement is so you can save the results to it if more than one name is found; (..) allows this as it turns the variable assignment into an expression having the output pass through onto the pipeline where it is either empty, or not.

Finally, referencing the $quser variable we can convert the strings into objects piping to ConvertFrom-Csv. Only step left to do is iterate through each row and passing it over to LogOff to perform the actual logoff.

If you've noticed, the headers are manually-specified because it is filtered out by the Where-Object cmdlet. This is a better approach seeing as there could be "more than one" RDP Session, now you're just left with those sessions matching the name which can be saved to $quser, so no extra filtering is needed down the line.