Managing INI files with PowerShell

Tue, Oct 2, 2007 4-minute read

The question came up on the newsgroup a few days ago on how to work with INI files from PowerShell.

A lot of great answers came up (using text parsing of the INI files,) but the Windows API actually supports reading and writing of INI file entries directly through its GetPrivateProfileString and WritePrivateProfileString functions. PowerShell doesn’t support P/Invoke to the Win32 API directly, but the Invoke-Win32 script given here does: http://www.leeholmes.com/blog/GetTheOwnerOfAProcessInPowerShellPInvokeAndRefOutParameters.aspx.

Since it’s reusable, that code sits better as a script of its own, named Invoke-WindowsApi (below.)

##############################################################################
##
## Invoke-WindowsApi.ps1
##
## From PowerShell Cookbook (O'Reilly)
## by Lee Holmes (http://www.leeholmes.com/guide)
##
## Invoke a native Windows API call that takes and returns simple data types.
##
## ie:
##
## ## Prepare the parameter types and parameters for the 
## CreateHardLink function
## $parameterTypes = [string], [string], [IntPtr]
## $parameters = [string] $filename, [string] $existingFilename, [IntPtr]::Zero
## 
## ## Call the CreateHardLink method in the Kernel32 DLL
## $result = Invoke-WindowsApi "kernel32" ([bool]) "CreateHardLink" `
##     $parameterTypes $parameters
##
##############################################################################
param(
    [string] $dllName, 
    [Type] $returnType, 
    [string] $methodName,
    [Type[]] $parameterTypes,
    [Object[]] $parameters
    )

## Begin to build the dynamic assembly
$domain = [AppDomain]::CurrentDomain
$name = New-Object Reflection.AssemblyName 'PInvokeAssembly'
$assembly = $domain.DefineDynamicAssembly($name, 'Run')
$module = $assembly.DefineDynamicModule('PInvokeModule')
$type = $module.DefineType('PInvokeType', "Public,BeforeFieldInit")

## Go through all of the parameters passed to us.  As we do this,
## we clone the user's inputs into another array that we will use for
## the P/Invoke call.  
$inputParameters = @()
$refParameters = @()

for($counter = 1; $counter -le $parameterTypes.Length; $counter++)
{
   ## If an item is a PSReference, then the user 
   ## wants an [out] parameter.
   if($parameterTypes[$counter - 1] -eq [Ref])
   {
      ## Remember which parameters are used for [Out] parameters
      $refParameters += $counter

      ## On the cloned array, we replace the PSReference type with the 
      ## .Net reference type that represents the value of the PSReference, 
      ## and the value with the value held by the PSReference.
      $parameterTypes[$counter - 1] = 
         $parameters[$counter - 1].Value.GetType().MakeByRefType()
      $inputParameters += $parameters[$counter - 1].Value
   }
   else
   {
      ## Otherwise, just add their actual parameter to the
      ## input array.
      $inputParameters += $parameters[$counter - 1]
   }
}

## Define the actual P/Invoke method, adding the [Out]
## attribute for any parameters that were originally [Ref] 
## parameters.
$method = $type.DefineMethod($methodName, 'Public,HideBySig,Static,PinvokeImpl',
    $returnType, $parameterTypes)
foreach($refParameter in $refParameters)
{
   [void] $method.DefineParameter($refParameter, "Out", $null)
}

## Apply the P/Invoke constructor
$ctor = [Runtime.InteropServices.DllImportAttribute].GetConstructor([string])
$attr = New-Object Reflection.Emit.CustomAttributeBuilder $ctor, $dllName
$method.SetCustomAttribute($attr)

## Create the temporary type, and invoke the method.
$realType = $type.CreateType()

$realType.InvokeMember($methodName, 'Public,Static,InvokeMethod', $null, $null, 
    $inputParameters)

## Finally, go through all of the reference parameters, and update the
## values of the PSReference objects that the user passed in.
foreach($refParameter in $refParameters)
{
   $parameters[$refParameter - 1].Value = $inputParameters[$refParameter - 1]
}

Using this script, you can easily wrap these APIs in a more friendly PowerShell scripts.

##############################################################################
##
## Get-PrivateProfileString.ps1
##
## Get an entry from an INI file.
##
## ie:
##
##  PS >Get-PrivateProfileString.ps1 C:\winnt\system32\ntfrsrep.ini text DEV_CTR_24_009_HELP
##
##############################################################################
param(
    $file,
    $category,
    $key)

## Prepare the parameter types and parameter values for the Invoke-WindowsApi script
$returnValue = New-Object System.Text.StringBuilder 500
$parameterTypes = [string], [string], [string], [System.Text.StringBuilder], [int], [string]
$parameters = [string] $category, [string] $key, [string] "", 

   [System.Text.StringBuilder] $returnValue, [int] $returnValue.Capacity, [string] $file
## Invoke the API
[void] (Invoke-WindowsApi "kernel32.dll" ([UInt32]) "GetPrivateProfileString" `

   $parameterTypes $parameters)
## And return the results
$returnValue.ToString()

and

##############################################################################
##
## Set-PrivateProfileString.ps1
##
## Set an entry from an INI file.
##
## ie:
##
##  PS >copy C:\winnt\system32\ntfrsrep.ini c:\temp\
##  PS >Set-PrivateProfileString.ps1 C:\temp\ntfrsrep.ini text `
##  >> DEV_CTR_24_009_HELP "New Value"
##  >>
##  PS >Get-PrivateProfileString.ps1 C:\temp\ntfrsrep.ini text DEV_CTR_24_009_HELP
##  New Value
##  PS >Set-PrivateProfileString.ps1 C:\temp\ntfrsrep.ini NEW_SECTION `
##  >> NewItem "Entirely New Value"
##  >>
##  PS >Get-PrivateProfileString.ps1 C:\temp\ntfrsrep.ini NEW_SECTION NewItem
##  Entirely New Value
##
##############################################################################
param(
    $file,
    $category,
    $key,
    $value)

## Prepare the parameter types and parameter values for the Invoke-WindowsApi script
$parameterTypes = [string], [string], [string], [string]
$parameters = [string] $category, [string] $key, [string] $value, [string] $file

## Invoke the API
[void] (Invoke-WindowsApi "kernel32.dll" ([UInt32]) `
    "WritePrivateProfileString" $parameterTypes $parameters)

Lee Holmes

Managing INI files with PowerShell

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