Monday, November 03, 2014

Reading the Windows PowerShell Language Specification Version 3.0

Anytime I spend a good deal of time with a technology, I eventually track down the core documentation. The real technical stuff that shows you everything. I just rediscovered the Windows PowerShell Language Specification Version 3.0. It would be nice to have one for PowerShell 4.0, but I did not see it yet. I rediscovered a few things that I either missed before or I was not ready to understand them yet. Here are some hidden gems that I would like to share with you.

Wildcard attributes
We use these all the time for partial matches. The cool thing is that we can use them in file paths to skip over folders that may have any name. Let me show you how we can use this to fix an old problem of mine.

Our home folders are also the users my documents folder. Every time a user logs in, they create a desktop.ini file in that location. It does this cool trick of renaming the folder to say "My Documents". This is nice, unless you are an admin looking a list of 500 folders called "My Documents". Here is a quick fix to delete all of those files.

Get-ChildItem d:\profile\*\desktop.ini | Remove-Item -Force

ForEach-Object -Member
I can't say that I have many uses for this one, but I think it is interesting. The ForEach-Object has a -MemberName property. If you provide it an objects function name, it will call it for each object. Here is one good example of using it to uninstall software.

Get-WMIObject Win32_Product | Where-Object name -match Java | ForEach-Object -MemberName Uninstall

Or we can shorthand this same command even more like this:

gwmi win32_product | ? name -match Java | % uninstall

This variable contains a dictionary of all the parameters that were passed to the function or script. The cool thing is that you can splat these to another function. This would be great when you are creating a wrapper around a function that takes lots of parameters. I don;t have a good example off hand, but I know I have code out there that would be much cleaner with this

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