#requires -version 2.0

<#
 -----------------------------------------------------------------------------
 Script: Test-ServicePack.ps1
 Version: 1.0
 Author: Jeffery Hicks
    http://jdhitsolutions.com/blog
    http://twitter.com/JeffHicks
    http://www.ScriptingGeek.com
 Date: 2/15/2012
 Keywords:
 Comments:

 "Those who forget to script are doomed to repeat their work."

  ****************************************************************
  * DO NOT USE IN A PRODUCTION ENVIRONMENT UNTIL YOU HAVE TESTED *
  * THOROUGHLY IN A LAB ENVIRONMENT. USE AT YOUR OWN RISK.  IF   *
  * YOU DO NOT UNDERSTAND WHAT THIS SCRIPT DOES OR HOW IT WORKS, *
  * DO NOT USE IT OUTSIDE OF A SECURE, TEST SETTING.             *
  ****************************************************************
 -----------------------------------------------------------------------------
 #>
 


Function Test-ServicePack {

<#
.Synopsis
Test Service Pack version value
.Description
Test if the service pack major version is equal or greater than
the specified version. By default the function will return True
or False. But you can use -Detail to retrieve additional system
and service pack information.

Computername            : CLIENT22
OperatingSystem         : Microsoft Windows 7 Professional 
ServicePackMajorVersion : 1
ServicePack             : Service Pack 1
OK                      : True

If you want to test for a specific service pack version, use the
-Exact parameter.
.Parameter Computername
The name of the computer to query. The default is the localhost.
.Parameter Version
The minimum service pack version.
.Parameter Exact
Test for an exact match with the service pack major version.
.Parameter Detail
If specified, return additional operating system and servicepack
information.
.Example
PS C:\>  test-servicepack server01 -version 1
True
.Example
PS C:\>  test-servicepack Client22 -version 1 -detail
Computername            : CLIENT22
OperatingSystem         : Microsoft Windows 7 Professional 
ServicePackMajorVersion : 1
ServicePack             : Service Pack 1
OK                      : True
.Example
PS C:\>  get-content computers.txt | test-servicepack -version 2 -detail | Where {!$_.OK} | Select Computername,ServicePackMajorVersion
Computername                 ServicePackMajorVersion
------------                 -----------------------
SERVER1                                            1
SERVER5                                            1

Go through the list of computers and test for at least service pack 1. 
Display computers that don't meet the criteria.
.Link
Get-WMIObject
#>

[cmdletbinding()]

Param (
[Parameter(Position=0,ValueFromPipeline=$True)]
[ValidateNotNullOrEmpty()]
[Alias("name")]
[string]$Computername=$env:computername,
[Parameter(Position=1)]
[int]$Version=0,
[switch]$Exact,
[switch]$Detail

)

Begin {
    Write-Verbose "Starting $($myinvocation.mycommand)"
    #a subset of WMI Properties to retrieve
    $props="ServicePackMajorVersion","CSName","CSDVersion","Caption"
}

Process {
    Write-Verbose "Getting OS information from $computername"

    Try {
        $OS=Get-WmiObject -Class Win32_OperatingSystem -Property $props -ComputerName $computername -ErrorAction Stop
        Write-verbose ("Testing SP version of {0}" -f $OS.Caption)
        if ($Exact) {
            Write-Verbose "Testing for exact match"
            $pass=$OS.ServicePackMajorVersion -eq $Version
        }
        else {
            Write-Verbose "Testing for at least version $Version"
            $pass=$OS.ServicePackMajorVersion -ge $Version
        }
        
        #write details if specified
        if ($Detail) {
            $os | Select @{Name="Computername";Expression={$_.CSName}},
            @{Name="OperatingSystem";Expression={$_.Caption}},
            ServicePackMajorVersion,
            @{Name="ServicePack";Expression={$_.CSDVersion}},
            @{Name="OK";Expression={$Pass}}
        }
        else {
            Write $pass
        }

    } #Try

    Catch {
        $msg="Failed to retrieve OS information from {0}. {1}." -f $computername.toUpper(),$_.exception.message
        Write-Warning $msg
    } #catch

    Finally {
        #clean up before next computer
        if ($OS) {
          Remove-Variable OS
        }
    } #finally
    
} #process

End {
    Write-Verbose "Ending $($myinvocation.mycommand)"
}

} #close function