How To Use If Else In Where-Object Powershell - powershell

Question

I am attempting to search HotFixes installed on a machine and pipe the machine name with the specified KB installed to an excel sheet "else" pipe the machine names without the KB installed to another excel sheet.
I've gotten the basic command down that will do this but because it uses the % (foreach) command, it is appending the machine name to the excel sheet for each KB it finds or doesn't find and I end up with dozens of duplicates.
How can I get this code to append a single entry for each search through all the KBs and not for each KB?
Get-HotFix | %{if($_.HotFixID -match "KB2687455"){(get-wmiobject win32_computersystem).name | Out-File C:\Installed.txt -append}` else{(get-wmiobject win32_computersystem).name | Out-File C:\NotInstalled.txt -Append}}
EDIT:
I have found a work around. Instead of trying to do this in a command line type of code I rewrote the code and surprisingly it worked. Let me know if you see any potential issues with this code.
if (Get-HotFix |?{$_.HotFixID -match "KB2687455"}) {
(get-wmiobject win32_computersystem).name | out-file C:\Installed.txt
}
else {
(get-wmiobject win32_computersystem).name | out-file C:\NotInstalled.txt
}

Answer 1

You are looping over the hot fixes that are installed, and writing results for each hot fixes when it looks like all you want to do is write whether a given machine has a hot fix installed or not. I'm assuming you will be running this on multiple machines and that the output file will be on a network share.
You need to break out of your else block after the initial pass:
Get-HotFix | % {
if ($_.HotFixID -match "KB2687455") {
(get-wmiobject win32_computersystem).name | Out-File C:\temp\Installed.txt -append
}
else
{
(get-wmiobject win32_computersystem).name | Out-File C:\temp\NotInstalled.txt -Append
break
}
}