Posts Tagged ‘Add-Type’

In PowerShell, cmdlets like Get-ChildItem and Get-Content support a -Credential parameter so you can access resources that require you to log in… the problem is that the built-in FileSystem provider does not. So as an example, if you have a server on a different domain and you want to copy files off of it, you can’t do this:

That will throw an error: “Cannot retrieve the dynamic parameters for the cmdlet. The provider does not support the use of credentials. Perform the operation again without specifying credentials.”

Impersonation

To solve this problem at work, I’ve written an impersonation module. It basically has two methods: Push-ImpersonationContext and Pop-ImpersonationContext. There is one catch: you need to be running in single-threaded apartment mode for it to work, because the impersonation only affects the current thread (if you’re not running PowerShell.exe -STA, your commands execute on a thread pool, so you never know from one to the next what thread you’ll be on). In any case, you use it like this:

It’s really very simple, and works great for when you need to access resources across multiple domains. Particularly files, for which PowerShell doesn’t support alternate credentials at all. Anyway the module code is on PoshCode, save it to your Documents\WindowsPowerShell\Modules\Impersonation\Impersonation.psm1 and use Import-Module Impersonation to load it. Here you go:

So earlier today someone asked how they could tell if PowerBoots graphics would be hardware accelerated on their system … and I found the question painful to answer because the answer is that you take the high-order word of the RenderCapability.Tier property, and that indicates 0, 1, or 2 … where a higher number indicates a higher level of hardware acceleration:

• Rendering Tier 0 No graphics hardware acceleration. The DirectX version level is less than version 7.0.
• Rendering Tier 1 Partial graphics hardware acceleration. The DirectX version level is greater than or equal to version 7.0, and lesser than version 9.0.

• Rendering Tier 2 Most graphics features use graphics hardware acceleration. The DirectX version level is greater than or equal to version 9.0.

The problem is that in PowerShell, getting the “high-order word” of an integer is a little annoying, because the normal way to do that is to right-shift the integer to throw away the low-order word … and PowerShell is missing the shift operators. Why? I don’t know. In any case, I figured, well, I’ll just write it as a function with a call out to C# to make my life simpler. The one catch is that the Add-Type cmdlet that lets you inject C# classes is new in PowerShell 2.0, so if you want to use this script in PowerShell 1.0 you need to get the New-Type function from PoshCode and replace Add-Type with New-Type in the script.

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