My new PowerShell install script

I wanted to write a PowerShell script that can execute common activities involved in deploying software. We require signed PowerShell scripts, so it was not practical to rewrite the script for every piece of software. Instead, I moved the configuration to an XML file.

The first function below takes an object (pulled from the XML config file) that contains the uninstall information. The scenario would be that you want to uninstall a piece of software before you install something else. First I try to remove the software via WMI. If that fails, I lookup the uninstall string and use msiexe.exe to try and uninstall the software bassed on the GUID of the software.

function UninstallStep ($Step)
{
    $CurrentDisplayName= $Step.CurrentDisplayName.Value
    $CurrentVersion= $Step.CurrentVersion.Value
      gwmi win32_product -filter "Name like '%$CurrentDisplayName%'" | foreach {
        $InstalledVersion = $_.Version
        if ($InstalledVersion -ne  $CurrentVersion) {
            write-host "Trying to uninstall $CurrentDisplayName $InstalledVersion via WMI"
	        if ($_.uninstall().returnvalue -eq 0) { write-host "Successfully uninstalled $CurrentDisplayName $InstalledVersion via WMI" }
	        else {
                write-host "WMI uninstall retured an error, Trying to uninstall $CurrentDisplayName $InstalledVersion from registry entries"
	            if (-not(Test-Path ("Uninstall:"))){New-PSDrive -name Uninstall -psprovider registry -root HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall | Out-Null}
	            Get-ChildItem -Path Uninstall: | Where-Object -FilterScript { $_.GetValue("DisplayName") -like "*$CurrentDisplayName*"} | ForEach-Object -Process {
	                $CommandToRun = "msiexec"
	                $UNSTring = $_.GetValue("UninstallString").split("{")
	                $Parameters = "/X /Q {" + $UNSTring[1]
	                write-host "Running Command: " $CommandToRun $Parameters
	                Start-Process $CommandToRun $Parameters -wait -workingdirectory $WorkingDirectory | out-null
	            }
	            }
        }
    }
}

Second piece of code is a generic command to run script. This is basically just a wrapper for the Start-Process command. It can be used to run any command, but mostly I use this to start the msiexec.exe program with parameters. I can also use this command to start an setup.exe. Again, this is read from the config.xml. If there are arguments, then the second part of the conditional runs.

Function CommandToRunStep ($Step)
{
  if ($Step.Command.Value -ne "") {
    $Command = $Step.Command.Value
    if ($Step.Arguments.Value -ne "") {
      $Arguments = $Step.Arguments.Value
      write-host "Running Command: " "$Command" "$Arguments"
      Start-Process "$Command" -ArgumentList "$Arguments" -wait -workingdirectory $WorkingDirectory | out-null
    }
    Else {
      write-host "Running Command: " "$Command"
      Start-Process -FilePath "$Command" -wait -workingdirectory $WorkingDirectory | out-null
    }
  }
}

The final function takes a process name from the config xml file and kills it.

function KillStep ($Step)
{
    $ProcessName= ($Step.ProcessName.Value).split(".")[0]
    if ($ProcessName -ne "") {

    write-host "Killing: " "$ProcessName"
    Stop-Process -force -processname "$ProcessName" -ea SilentlyContinue
    }
}

The main part of this script loops through the xml file and call the correct function. The xml file can contain any number of the three types of functions above, and they are run in sequential order. This gives me the ability to create a “task sequence” in an xml file that will be run with a PowerShell script in an SCCM advertised program.

#  Main
$WorkingDirectory = Split-Path -parent $MyInvocation.MyCommand.Definition
[ xml ]$s = Get-Content $WorkingDirectory\Install.xml

foreach ($Step in $s.Install.Steps.Step)
{
switch ($Step.StepType.Value)
    {
    "UninstallOlderThan" {UninstallStep ($Step)}
    "CommandToRun" {  CommandToRunStep ($Step)}
    "KillProcess" { KillStep ($Step) }
    }
}

Updated
And an example of the XML file would be:

<Install>
<Steps>
  <Step>
	<StepType Value="UninstallOlderThan" />
	<CurrentDisplayName value="Apple Application Support" />
    	<CurrentVersion value="1.3.3" />
  </Step>
  <Step>
	<StepType Value="CommandToRun" />
	<Command Value="msiexec" />
	<Arguments Value="/i AppleApplicationSupport.msi /quiet /norestart" />
  </Step>
  <Step>
	<StepType Value="CommandToRun" />
	<Command Value="iTunesSetup.exe" />
	<Arguments Value="/quiet DESKTOP_SHORTCUTS=0" />
  </Step>
  <Step>
	<StepType Value="KillProcess" />
	<ProcessName Value="Process.exe" />
  </Step>
</Steps
</Install>