Guy's Scripting Ezine 94 - What WMI can do for You

Guy recommends this:
Free - WMI Monitor

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Guy's Top 10 Free Tools

1) FreePing
2) Network Monitor
3) Xobni
4) PuTTY (UNIX)
5) WMI Monitor
6) BgInfo
7) Net-SNMP
8) Engineer's Toolset
9) Exchange Monitor
10) WinDiff

Contents for Ezine 94 - What WMI can do for You

• This Week's Secret
• What can WMI do for you?
• WMI Methods and Mission
• Learning Points
• Summary of WMI

This Week's Secret

Can I write an ebook on WMI (Windows Management Instrumentation) in a week?  Given my other commitments, probably not.  Can I write a WMI ebook in a fortnight?  Watch this space!  I will give it a try.

What WMI can do for You

This week I want to help you get started with WMI.  The keyword in the acronym WMI is instrumentation.  Microsoft provide us with all the tools, objects and methods, it is up to you and I to make best use of these instruments.  Now for the key questions.

Why, is always a good question.  Why write WMI scripts?   The answer is because you want information or control.  For instance, the ultimate skill with Group Policies is to apply WMI filters so that only machines, which match your specifications, get the policy.  By specification I mean, Disk space, memory or operating system.

Another reason for writing WMI is scripts is that you require hardware inventories.  For example, how many of our computers chassis are Desktops and how many are 'Pizza Boxes'? What are the cooling fans' specifications on the servers?  Who are the disk manufacturers of our servers in the branch office?  How much L2 Cache does our CPU have?

Perhaps the best question of all is, what can we do to harness the power of WMI?  The answer to that is either create a do-it-yourself script, or call for some level of help.  Scriptomatic is a good place to start, it's free and Scriptomatic is the script engine of more expensive tools.  If you have already invested in the OnScript editor, check out their free Scriptomatic add-on.  If you have not bought OnScript then I recommend that you get a free trial of this wonderful script editor.

If you are looking for handy network utilities, try some of the free downloads at Tools4Ever

WMI Methods and Mission

Whereas logon scripts have only one object (network) and a handful of methods, for example, MapNetworkDrive and AddPrinterConnection, WMI has tens of objects and hundreds of methods.

The idea behind this week's VBScript is to interrogate the operating system and discover the chassis type.  I have to admit that previously, I did not realize the variety of different chassis types.  Not only are there Desktop and Laptop, but also 'Pizza Box' and 'Lunch Box'. However, my real mission is to introduce to the WMI components.  Please realize that you could substitute any of the WMI classes below for Win32_SystemEnclosure.  I admit that you would need Scriptomatic to identify the correct properties for whichever class you choose.

Obvious Counters.

1. Win32_PhysicalMemory - not Win32_Memory.
2. Win32_Processor - Clock Speed, Voltage, Cache size
3. Win32_DiskDrive - Physical Disk data. Based on the number of blocks, tracks or sectors.
4. Win32_LogicalDisk - Partition size, Drive Type and FreeSpace.

More WMI Counters

Many of these WMI Classes need a filter for example: 
For Each objChassis in colChassis
  For Each objItem in objChassis.ChassisTypes
Without a filter you get swamped with data.  However, I want to begin by giving you the broadest possible perspective, so here is a list of useful classes, each with ten or more properties.

1. Win32_SystemEnclosure - What type of chassis does your computer have?  See this week's script.
2. Win32_Keyboard - Worth a look.
3. Win32_LoadOrderGroup - More services than I anticipated.
4. Win32_LoggedOnUser - More accounts than I predicted.
5. Win32_PointingDevice - Reminds me HID means Human Interface Device.
6. Win32_Product - Check software installed.  Ideas for checking viruses?
7. Win32_SystemBios - See if there have been upgrades.
8. Win32_SystemOperatingSystem - Boot partition information.
9. Win32_TimeZone - Not quite what I thought.  Displays the months, days and hours when the clocks spring forward or fall back.
10. Win32_VideoSettings - Disappointing.  Displays all possible values rather than current settings.

Instructions for Creating a WMI script to Discover the Chassis Type

1. Logon as a local Administrator.
2. Copy and paste the example script below into notepad or use a VBScript editor.
3. Save the file with a .vbs extension, for example: Chassis.vbs 
4. Double click and check machine's chassis type.
5. Optional suggestion edit strComputer = "." to the NetBIOS name of another computer.

Learning Points

Note 1:  Consider this section of the script.

Set objWMIService = GetObject("winmgmts:" _
& "{impersonationLevel=impersonate}!\\" _
& strComputer & "\root\cimv2")

The above phrase is standard in so many WMI scripts.  What it says in plain English is, connect to the heart of the WMI namespace.  {impersonationLevel=impersonate} is one of those commands that I just accept is necessary.  In fact, it reminds me to logon as an administrator so that the script will not fail for the trivial reason of insufficient user rights.

Note 2:  Set colChassis = objWMIService.ExecQuery _
("Select * from Win32_SystemEnclosure",,16)

As ever, note the verbs.  Firstly, ExecQuery which says carry out the request.  Select * is famous in all query languages, get all. 

Note 3:  Identify the class - Win32_SystemEnclosure.  The Win32_xyz class is the first place that I look to see the purpose of a particular script.  SystemEnclosure means the computer 'Box', 'Unit', the chassis type.

Note 4: This script employs two loops.  The phrase 'col' means collation.  WMI scripts interrogate a whole collection of properties, for this example I have singled out objChassis.ChassisTypes.

Note 5:  I never miss an opportunity to showcase the 'Select Case' construction.  Multiple 'Else If' would be ungainly, whereas Select Case works elegantly.

Note 6:  Edit strComputer = "." and substitute the name of another machine on your network.  If you accept this challenge, uncomment the last but 3 line.

Summary of WMI

Remember that the operating system knows everything.  Thank Microsoft for providing a library of WMI commands with which to interrogate systems like the Event Logs.  WMI scripting is tricky because there are so many elements.  Take the time to have a walk through of how you examine an Event Log property sheet.  In particular, match the Event ID, Success or Failure and type of Log with variables in my script.

Guy Thomas recommends Computer Training Software. 

Their topics and material are ideal for getting you started with VBScript.  The videos are easy to follow and you can control the pace.  Try their free demo material and then see if you want to buy the full package. See more about VB Script Training CD.

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