Test if registry value exists

Question

In my powershell script I m creating one registry entry for each element I run script on and I would like to store some additional info about each element in registry  if you specify optional parameters once then by default use those params in the future    The problem I ve encountered is that I need to perform Test-RegistryValue  like here--see comment  but it doesn t seem to do the trick  it returns false even if entry exists   I tried to  build on top of it  and only thing I came up is this   Function Test-RegistryValue  regkey   name         try                exists   Get-ItemProperty  regkey  name -ErrorAction SilentlyContinue         Write-Host  Test-RegistryValue   exists          if    exists -eq  null  -or   exists Length -eq 0                         return  false                   else                       return  true                     catch               return  false           That unfortunately also doesn t do what I need as it seems it always selects some  first   value from the registry key   Anyone has idea how to do this  It just seems too much to write managed code for this

User · Answer

The -not test should fire if a property doesn t exist    prop    Get-ItemProperty  regkey   name if  -not  prop       New-ItemProperty -Path  regkey -Name  name -Value  X

User · Answer

Probably an issue with strings having whitespace   Here s a cleaned up version that works for me   Function Test-RegistryValue  regkey   name         exists   Get-ItemProperty -Path   regkey  -Name   name  -ErrorAction SilentlyContinue     If    exists -ne  null  -and   exists Length -ne 0             Return  true           Return  false

User · Answer

The Carbon PowerShell module has a Test-RegistryKeyValue function that will do this check for you    Disclosure  I am the owner maintainer of Carbon    You have to check that that the registry key exists  first   You then have to handle if the registry key has no values   Most of the examples here are actually testing the value itself  instead of the existence of the value   This will return false negatives if a value is empty or null   Instead  you have to test if a property for the value actually exists on the object returned by Get-ItemProperty   Here s the code  as it stands today  from the Carbon module   function Test-RegistryKeyValue        lt        SYNOPSIS     Tests if a registry value exists        DESCRIPTION     The usual ways for checking if a registry value exists don t handle when a value simply has an empty or null value   This function actually checks if a key has a value with a given name        EXAMPLE     Test-RegistryKeyValue -Path  hklm  Software Carbon Test  -Name  Title       Returns  True  if  hklm  Software Carbon Test  contains a value named  Title     False  otherwise        gt       CmdletBinding        param           Parameter Mandatory  true            string            The path to the registry key where the value should be set   Will be created if it doesn t exist           Path            Parameter Mandatory  true            string            The name of the value being set           Name            if  -not  Test-Path -Path  Path -PathType Container                  return  false             properties   Get-ItemProperty -Path  Path      if  -not  properties                 return  false             member   Get-Member -InputObject  properties -Name  Name     if   member                 return  true           else               return  false

User · Answer

regkeypath   HKCU  SOFTWARE Microsoft Windows CurrentVersion Run    value1    Get-ItemProperty  regkeypath -ErrorAction SilentlyContinue  Zoiper -eq  null  If   value1 -eq  False    Write-Host  Value Exist    Else   Write-Host  The value does not exist

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My version  matching the exact text from the caught exception  It will return true if it s a different exception but works for this simple case  Also Get-ItemPropertyValue is new in PS 5 0  Function Test-RegValExists  Path   Value    ee         Exception catcher try      Get-ItemPropertyValue -Path  Path -Name  Value   Out-Null      catch  ee             if   ee Exception Message -match  Property  Value does not exist   return  false  else  return  true

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Personally  I do not like test functions having a chance of spitting out errors  so here is what I would do   This function also doubles as a filter that you can use to filter a list of registry keys to only keep the ones that have a certain key   Function Test-RegistryValue       param           Alias  PSPath             Parameter Position   0  Mandatory    true  ValueFromPipeline    true  ValueFromPipelineByPropertyName    true            String  Path                    Parameter Position   1  Mandatory    true            String  Name                    Switch  PassThru             process           if  Test-Path  Path                 Key   Get-Item -LiteralPath  Path             if   Key GetValue  Name   null  -ne  null                    if   PassThru                        Get-ItemProperty  Path  Name                   else                        true                                 else                    false                         else                false

User · Answer

If you are simply interested to know whether a registry value is present or not then how about    bool   Get-itemproperty -Path  HKLM  SOFTWARE Microsoft Windows NT CurrentVersion   PathName    will return   true while   bool   Get-itemproperty -Path  HKLM  SOFTWARE Microsoft Windows NT CurrentVersion   ValueNotThere    will return   false as it s not there     You could adapt it into a scriptblock like    CheckForRegValue     Param  String  KeyPath   String  KeyValue  return  bool   Get-itemproperty -Path  KeyPath   KeyValue      and then just call it by    amp   CheckForRegValue  HKLM  SOFTWARE Microsoft Windows NT CurrentVersion  PathName   Have fun   Porky

User · Answer

The best way to test if a registry value exists is to do just that - test for its existence   This is a one-liner  even if it s a little hard to read      PS C    Get-ItemProperty  regkey  PSObject Properties Name -contains    name   If you actually look up its data  then you run into the complication of how Powershell interprets 0

User · Answer

This works for me   Function Test-RegistryValue        param  regkey   name       exists   Get-ItemProperty   regkey  name  -ErrorAction SilentlyContinue     Write-Host  Test-RegistryValue   exists      if    exists -eq  null  -or   exists Length -eq 0                 return  false           else               return  true

User · Answer

I would go with the function Get-RegistryValue  In fact it gets requested values  so that it can be used not only for testing   As far as registry values cannot be null  we can use null result as a sign of a missing value  The pure test function Test-RegistryValue is also provided     This function just gets  true or  false function Test-RegistryValue  path   name         key   Get-Item -LiteralPath  path -ErrorAction SilentlyContinue      key -and  null -ne  key GetValue  name   null       Gets the specified registry value or  null if it is missing function Get-RegistryValue  path   name         key   Get-Item -LiteralPath  path -ErrorAction SilentlyContinue     if   key             key GetValue  name   null             Test existing value Test-RegistryValue HKCU  Console FontFamily  val   Get-RegistryValue HKCU  Console FontFamily if   val -eq  null     missing value    else    val      Test missing value Test-RegistryValue HKCU  Console missing  val   Get-RegistryValue HKCU  Console missing if   val -eq  null     missing value    else    val     OUTPUT   True 54 False missing value

User · Answer

One-liner    valueExists    Get-Item  regKeyPath -EA Ignore  Property -contains  regValueName

User · Answer

I took the Methodology from Carbon above  and streamlined the code  into a smaller function  this works very well for me       Function Test-RegistryValue  key  name                 if Get-Member -InputObject  Get-ItemProperty -Path  key  -Name  name                            return  true                     return  false

User · Answer

My version   Function Test-RegistryValue  Key   Name         Get-ChildItem  Split-Path -Parent -Path  Key    Where-Object     PSChildName -eq  Split-Path -Leaf  Key    Property -contains  Name

[powershell] Test if registry value exists

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