Wednesday, April 2, 2008

Windows PowerShell

Started spending some time with Windows PowerShell, an next generation command shell and scripting environment for Windows. It can be downloaded from Microsoft's site. It's essentially finally an update to the classic DOS commands, providing simple commands for interacting with WMI, the file system, the registry, etc. The syntax is closer to .Net, and return values are actually rich .net data types.

After PowerShell is installed, you get a new 'console' (type 'powershell' in the run box to access) The syntax of PowerShell commands is verb-noun and has a fairly intuitive layout, I think this contrasts nicely from the DOS commands with vestiges of the 8.3 file names. In PowerShell, the following two commands will likely be the first you run:
    • get-command (lists all available commands)
    • get-help {command name} (lists further details on the given command)

DOS vs. VB Script vs. PowerShell
If DOS commands are the 1.0 version of an admin's 'console', powershell could be considered 2.0, and perhaps VBScript (or, yes, any WSH compatible scripting language) would be 1.5. While DOS relied on imperative commands, the admin using it didn't really have to 'think' like a programmer. To do any work with the file system or registry, without having a very obscure DOS batch file, VBScript had to be used. Also to do any work with WMI, VBScript had to be used. However to use VBScript, the admin really did have to think like a programmer, with looping, conditionals, object instantiation and disposal, etc. being for many tasks, critical for use. I've introduced a number of non-programmers to VBScript (WMI, etc.), and the barrier is two-fold, they have to learn the steps to accomplish the task at hand (i.e. retrieving, or setting something through WMI), as well as learn a modest amount of programming concepts they may have never dealt with. Sometimes that is a reason to stick with a DOS batch file to accomplish a step of the task, such as copying a file using 'xcopy' vs. using VBScript where the process may be more elegant and allow for more structure such as error handling (albeit in a rudimentary form)

PowerShell moves back to the DOS batch file type usage scenario, where an admin (non-programmer) can focus on the task at hand, with modest understanding of programming concepts , such as looping , conditionals and variables, and nearly no necessity of understanding objects lifetime concepts. In PowerShell, most commands return and accept objects as simply as they would accept string values.

The first advantage of PowerShell that struck me was the ease of interacting with WMI, even on a remote computers. Note that PowerShell is not a 'replacement' for WMI, any more that VBScript/WSH was WMI. WMI is still the underlying data structure to expose information about a computer. The syntax and library around it is what's changing here. The implicit functions (called cmdlets - "command-lets") provide much of it, and the adoption of a .net style syntax, where basically more stuff can be done on a single line of code helps

For example, this script I had sitting around to determine how much memory was on a remote computer
In VBScript:

strComputer = "ComputerB"
Set wbemServices = GetObject("winmgmts:\\"
& strComputer)
Set wbemObjectSet =

For Each wbemObject In wbemObjectSet
WScript.Echo "Total Physical Memory (kb): " &


In PowerShell:
Get-WmiObject Win32_LogicalMemoryConfiguration –computername ComputerB

Albeit, I'm not a fan of terse-ness for terse-ness sakes (or else we would just write everything in Perl :)), but the ability to have a single command do what the most obvious intent, and having the ability to send that output into other commands.

PowerShell is support in Windows XP or newer. However, at this point, PowerShell does not ship natively with any Microsoft OS, although it appears it will be an optional install on Windows Server 2008. Since it's not native on my client computers, I anticipate it primarily being used in admin 'push'-style scripts vs. something end-user facing.

At a very early glance, I'm seeing PowerShell replace the utility of DOS batch files and VBScript/WSH solutions as soon as the platforms ubiquitously support it. Right now, the barrier is computer running Windows 2000 or earlier (with no support for PowerShell), and the fact that even Windows XP computer already have support for DOS batch files and have WSH, while they don't have PowerShell.

For the short to mid-term, there will still be a number of DOS batch files and VBScript solutions for end-user facing needs: Functions that can run without admin privileges, ran by the user on demand, or during their log on or similar event. this will be simply because they most likely already have everything they need to run it.

However, for admin-driven scripts, where you as an IT person will be pushing something from your computer 'out' to other computers, or querying other computers, install PowerShell and try it out, starting with the replacements for some of the basic DOS commands you might now, and evolving into WMI and replacing your VBScript, if you have any. I think you will find it a productive environment to accomplish many common admin tasks.

In a future article, I will detail a line-by-line conversion from one of my more complex VBScripts into PowerShell, and also evaluate some of the PowerShell editors that provide some advanced edit/view features.

Further Reading
Free Windows PowerShell workbook: server administration
Windows PowerShell Getting Started Guide