I've been doing some work lately involving the registry and Windows PowerShell. One of the tasks was to create new registry keys and entries. But because I wanted to some robustness, I wanted a way to verify if a given key or entry already existed.<\/p>\n
Using Get-ItemProperty is the easy way to accomplish this.
\n[cc lang=\"PowerShell\"]
\nPS S:\\> get-itemproperty -Path HKCU:\\jdhit\\powershell -name test<\/p>\n
PSPath : Microsoft.PowerShell.Core\\Registry::HKEY_CURRENT_USER\\jdhit\\powershell
\nPSParentPath : Microsoft.PowerShell.Core\\Registry::HKEY_CURRENT_USER\\jdhit
\nPSChildName : powershell
\nPSDrive : HKCU
\nPSProvider : Microsoft.PowerShell.Core\\Registry
\nTest : Foo
\n[\/cc]
\nThis is just fine if it exists, but a pain if it doesn't.
\n[cc lang=\"PowerShell\"]
\nPS S:\\> get-itemproperty -Path HKCU:\\jdhit\\powershell -name bogus
\nGet-ItemProperty : Property bogus does not exist at path HKEY_CURRENT_USER\\jdhit\\powershell.
\nAt line:1 char:17
\n+ get-itemproperty <<<< -Path HKCU:\\jdhit\\powershell -name bogus\n + CategoryInfo : InvalidArgument: (bogus:String) [Get-ItemProperty], PSArgumentException\n + FullyQualifiedErrorId : System.Management.Automation.PSArgumentException,Microsoft.PowerShell.Commands.GetItemPr\n opertyCommand\n[\/cc]\nSo I ended up writing a wrapper function that returns True or False if the item exist. The function handles the error handling and also takes transactions into account, since that might be a factor when working with the registry.\n[cc lang=\"PowerShell\"]\nFunction Test-RegistryItem {\n\n<#\n.SYNOPSIS\n\tTest the the existence of a registry value\n\n.DESCRIPTION\n\tThis command will determine if a given registry key exists. You must specify a registry path\n\tand the name of the key. \n\n.PARAMETER Path\n\tThe registry path using the registry PSDrive format, ie HLKLM:\n\n.PARAMETER Property\n\tThe property name to check. The parameter as an alias of Name.\n\t\n.PARAMETER UseTransaction\n\tUse an active transaction. This parameter is valid only when a transaction is in progress.\n \tFor more information, see about_Transactions.\n\n.EXAMPLE\n\tPS C:\\> test-itemproperty -Path \"HKLM:\\Software\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon\" -Property \"Shell\"
\n\tTrue<\/p>\n
.INPUTS
\n\t[String]<\/p>\n
.OUTPUTS
\n\t[Boolean]<\/p>\n
.NOTES
\n NAME: Test-RegistryItem
\n AUTHOR: Jeffery Hicks
\n VERSION: 1.0
\n LASTEDIT: 10\/01\/2010<\/p>\n
Learn more with a copy of Windows PowerShell 2.0: TFM (SAPIEN Press 2010)<\/p>\n
.LINK
\n\tGet-ItemProperty
\n.LINK
\n\thttp:\/\/jdhitsolutions.com\/blog<\/p>\n
#><\/p>\n
[cmdletbinding()]<\/p>\n
Param (
\n\t[Parameter(Position=0,Mandatory=$True,HelpMessage=\"Enter a registry path using the PSDrive format.\")]
\n\t[ValidateNotNullOrEmpty()]
\n [string]$Path,<\/p>\n
\t[Parameter(Position=1,Mandatory=$True,HelpMessage=\"Enter a registry key name.\")]
\n\t[ValidateNotNullOrEmpty()]
\n\t[Alias(\"name\")]
\n [string]$Property,
\n [Switch]$UseTransaction
\n)
\n \tWrite-Verbose (\"Looking for {0} in {1}\" -f $Property,$Path)
\n if (Test-Path $path)
\n {
\n \tif ($UseTransaction)
\n \t{
\n \t\t$item=Get-ItemProperty -Path $path -Name $property -ErrorAction \"SilentlyContinue\" -UseTransaction
\n \t} else
\n \t{
\n \t\t$item=Get-ItemProperty -Path $path -Name $property -ErrorAction \"SilentlyContinue\"
\n \t}<\/p>\n
if ($item )
\n {
\n \t#display the item if using -Verbose
\n \tWrite-Verbose ($item | select * | Out-String)
\n $True
\n }
\n else
\n {
\n \tWrite-Verbose \"Not found\"
\n $False
\n }
\n }
\n else
\n {
\n Write-Warning \"Failed to find $path\"
\n $False
\n }<\/p>\n
} #end function
\n[\/cc]<\/p>\n
The function uses the same parameters as Get-ItemProperty, although it adds an extra step to verify that the registry path exists by using Test-Path. Now, I can easily test for a key.
\n[cc lang=\"PowerShell\"]
\nPS S:\\> test-registryitem -Path HKCU:\\jdhit\\powershell -name bogus
\nFalse
\nPS S:\\> test-registryitem -Path HKCU:\\jdhit\\powershell -name test
\nTrue
\n[\/cc]<\/p>\n