Get computername by username

I am trying to find a computername that is used by certain user.

To do it I get a list of computers by Get-ADComputer and then ask all of them if there is a user I am looking for logged on.

This is my script:

$pcs = Get-ADComputer -filter {name -like "prg1-7100002421" -and enabled -eq "true"} |  Select-Object name
foreach($pc In $pcs)
{
    if (@(Get-WmiObject -ComputerName $pc.name -Namespace root\cimv2 -Class Win32_ComputerSystem)[0].UserName -eq "ANT\username")
    {
        $pc.name
    }
}

If -like is my computer: "prg1-7100002421" then it works fine with output:

PRG1-7100002421

But if I set a range by * in -like like this:

$pcs = Get-ADComputer -filter {name -like "prg1-710000242*" -and enabled -eq "true"} |  Select-Object name
foreach($pc In $pcs)
{
    if (@(Get-WmiObject -ComputerName $pc.name -Namespace root\cimv2 -Class Win32_ComputerSystem)[0].UserName -eq "ANT\username")
    {
        $pc.name
    }
}

then output is:

Get-WmiObject : The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)
At C:\Users\lbartuse\Desktop\user to pc.ps1:4 char:8
+     if (@(Get-WmiObject -ComputerName $pc.name -Namespace root\cimv2 -Class Win32_C ...
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Get-WmiObject], COMException
    + FullyQualifiedErrorId : GetWMICOMException,Microsoft.PowerShell.Commands.GetWmiObjectCommand

PRG1-7100002421
Get-WmiObject : The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)
At C:\Users\lbartuse\Desktop\user to pc.ps1:4 char:8
+     if (@(Get-WmiObject -ComputerName $pc.name -Namespace root\cimv2 -Class Win32_C ...
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Get-WmiObject], COMException
    + FullyQualifiedErrorId : GetWMICOMException,Microsoft.PowerShell.Commands.GetWmiObjectCommand

Get-WmiObject : The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)
At C:\Users\lbartuse\Desktop\user to pc.ps1:4 char:8
+     if (@(Get-WmiObject -ComputerName $pc.name -Namespace root\cimv2 -Class Win32_C ...
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Get-WmiObject], COMException
    + FullyQualifiedErrorId : GetWMICOMException,Microsoft.PowerShell.Commands.GetWmiObjectCommand

Get-WmiObject : The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)
At C:\Users\lbartuse\Desktop\user to pc.ps1:4 char:8
+     if (@(Get-WmiObject -ComputerName $pc.name -Namespace root\cimv2 -Class Win32_C ...
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Get-WmiObject], COMException
    + FullyQualifiedErrorId : GetWMICOMException,Microsoft.PowerShell.Commands.GetWmiObjectCommand

Get-WmiObject : The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)
At C:\Users\lbartuse\Desktop\user to pc.ps1:4 char:8
+     if (@(Get-WmiObject -ComputerName $pc.name -Namespace root\cimv2 -Class Win32_C ...
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Get-WmiObject], COMException
    + FullyQualifiedErrorId : GetWMICOMException,Microsoft.PowerShell.Commands.GetWmiObjectCommand

it still works but it is full of errors.

By the way output of:

$pcs = Get-ADComputer -filter {name -like "prg1-710000242*" -and enabled -eq "true"} |  Select-Object name
foreach($pc In $pcs)
{
    $pc.name
}

is:

PRG1-7100002420
PRG1-7100002421
PRG1-7100002422
PRG1-7100002423
PRG1-7100002424
PRG1-7100002425
PRG1-7100002426
PRG1-7100002427
PRG1-7100002428
PRG1-7100002429

Am I missing something? Or is there a more direct way to find computername by username than asking all computers if there is a certain user logged on them? This approach is quite slow.

You are getting the errors from computers which inaccessible, ie switched off, firewalled or don't have the WMI(Winmgmt) service running. Use try/catch to nicely catch the errors by adding -ErrorAction Stop to your query:

foreach($pc In $pcs)
{   
    try{
        if (@(Get-WmiObject -ComputerName $pc.name -Namespace root\cimv2 -Class Win32_ComputerSystem -ErrorAction Stop )[0].UserName -eq "ANT\username")
        {
            $pc.name
        }
    }
    catch{
        Write-Host ($pc.name + " is inaccessible")
    }
}