Ezine 145 -
PowerShell Employs WMI to Interrogate Disks
PowerShell Employs WMI* to Interrogate Disks One key reason for switching from
VBScript to PowerShell is because PowerShell handles WMI* so much more easily than VBScript.
* (Windows Management Instrumentation)
Topics for WMI Interrogates Disks
♣
Did you ever stop and think about what your operating system must
know? In a word the operating system knows EVERYTHING. Normally
XP, Vista or Windows 2003 hides much of the detail from displaying in
the Windows Explorer shell and its numerous GUIs. WMI (Windows
Management Instrumentation) is a built-in technology, which provides us with
a way to retrieve technical detail from the operating system.
My WMI examples reminds me of climbing a mountain, there is more than
one route to the summit. Moreover, you could climb using a variety of
equipment, and you could even call for help from a guide.
This Week's Mission is to check how much free space is available on each
disk.
From the point of view of learning PowerShell, we really are diving in at
the deep-end. I admit that I am obsessed with finding scripts which do
useful work, rather than just show off clever scripting techniques.
The price we pay for this gung-ho approach is that some elements may be incomprehensible to the
beginner, however that is a risk worth taking. Also remember that I do
provide Learning Points to explain how the script achieves its goals.
As ever, if we break-down the task into individual elements, it is easier to
understand what is going on. My hope is that by dissecting my scripts
you can modify commands and improve them to fit your circumstances.
Objective 1: Get one of the WMI objects. As the acronym WMI (Windows Management
Instrumentation) suggests, this method probes the operating system; in our
disk
example WMI connects specifically to the win32_logicaldisk object.
Objective 2: We want PowerShell to report each disk's size and
free space.
To collect this data we can to issue a SQL query to the LogicalDisk.
In Example 2, observe the command: get-wmiobject
-query "Select.....".
Objective 3: Much of the rest of Examples 2 and 3 is concerned with
sorting the
data, and then formatting the output to produce a table to our liking.
Instructions:
Pre-requisite: Visit Microsoft's site and download the correct version of PowerShell for your operating system.
- Launch PowerShell
- Copy the lines of code below (into memory)
- Right-click on the PowerShell symbol
- Edit --> Paste
- Press enter to execute the code
- (Alternatively, just type the commands at the PowerShell prompt)
# Start of Example 1 clear-Host
get-WmiObject win32_logicaldisk
Example 1a: (Format) Table with automatic column width
# Start of Example 1a clear-Host
get-WmiObject win32_logicaldisk |format-Table -auto
Learning Points
Note 1: PowerShell commands are not case
sensitive. Get-wmiobject works as well as get-WmiObject. Note 2:
Observe PowerShell and WMI can display properties such as DriveType which do not display in Windows
Explorer
Guy
Recommends: WMI Monitor and It's Free!
Windows Management Instrumentation (WMI) is one of the hidden
treasures of Microsoft operating systems. Fortunately, Solarwinds
have created a
Free WMI Monitor so that you can discover these gems of performance
information, and thus improve your scripts. Take the guess work out of which WMI counters to use when scripting the
operating system, Active Directory or Exchange Server.
Download your free copy of WMI Monitor
Whenever you discover a new
PowerShell command such as get-wmiobject, it benefits from being surveyed
by what I call the 'Trusty Twosome': Get-Help and Get-Member. To see what I mean, try these two commands:
1) get-help Get-WmiObject
(help WmiObject -full)
I like the -full because it gives examples of the command. Get-help shows useful parameters such as: -query, -computername
and -credential
2)
get-wmiobject win32_logicaldisk |get-member -memberType property
(gwmi win32_logicaldisk | gm -membertype
property) This command reveals a list of properties that you can
incorporate in your scripts, for example: DeviceID and DriveType.
If you are looking for handy network utilities, try some of the free downloads at
Tools4Ever
# Start of Example 2 clear-Host
get-wmiobject -query "Select * from win32_logicaldisk" |sort mediatype |`
format-table DeviceId, DriveType, Size, FreeSpace -auto -groupby MediaType
Learning Points
Note 1: This example uses the powerful -query to
select (* all) properties from the win32_logicaldisk object. Note
2: Once selected, we can sort the data and even group the
disks in the output. Note 3: If you look carefully
you can see the backtick (`) at the end of line two. The purpose of this
tiny symbol is to tell
PowerShell that the same command continues on the next line. Example 3
(Better) Displaying FreeSpace as a percentage
# Start of Example 3 clear-Host
$Jumbo = 1024 * 1024 * 1024
"Disk: Free Space"
$DiskObj = get-WmiObject Win32_LogicalDisk | Where-Object { $_.DriveType -eq 3 }
$DiskObj | foreach { $_.DeviceID, (($_.freespace /$Jumbo) / ($_.size / $Jumbo))}
Learning Points
Note 1: This example does not use the -query
parameter. Instead it employs the where clause to filter the data and
pass the stream to the foreach loop, which display each disk drive.
Note 2: $Jumbo is a variable to assist with
converting the bytes to gigabytes. Note 3: My
purpose is to show you how flexible PowerShell is at achieving slightly
different objectives. (Remember my analogy with mountain climbing, many ways
of reaching the summit.)
Calculating IP Address
ranges is a black art, which many network managers solve by creating custom
Excel spreadsheets. IPAT cracks this problem of allocating IP addresses
in networks in two ways:
For Mr Organized there is a nifty subnet
calculator, you enter the network address and the subnet mask, then IPAT
works out the usable addresses and their ranges.
For Mr Lazy IPAT
discovers and then displays the IP addresses of existing computers.
Download the Free IP Address Tracker
# Start of Example 3a clear-Host
$Jumbo = 1024 * 1024 * 1024
"Disk: Freespace %"
$DiskObj = get-WmiObject Win32_LogicalDisk | Where-Object { $_.DriveType -eq 3 }
$DiskObj | foreach { "{0,5} {1,5} {2,10:p}" -f `
$_.DeviceID, [int]($_.freespace / $Jumbo), (($_.freespace /$Jumbo) / ($_.size /
$Jumbo))}
Learning Points
Note 1: Observe the -f formatting
technique. What -f does is give greater control over the column
widths. Each of the three pairs of {braces} represents a data item in
the last line. Another benefit of the -f formatting is to enable us to
display the results as a percentage {2,10:p}. Note 2: $Jumbo
is a variable to assist with converting bytes to gigabytes. I expect
you spotted the usual maths operators to divide (/) and display as whole
numbers [int]. Tip: Keep an eye on the type of
bracket. Whether PowerShell uses (parenthesis) {braces} or [square]
brackets is highly significant. As a rule of thumb these types of bracket
mean: (compulsory), {script block}, [optional]. Challenges
Challenge 1: Experiment with the display of Examples 1a
and 2, remove -auto. You could also try format-list instead of
format-table. Challenge 2: In Example 3a, edit the
properties, for example, change [int]($_.freespace / $Jumbo), to ($_.freespace
/ $Jumbo) Challenge 3: In Example 2 attempt to alter the
'Sort' and '-groupby' criteria.
Summary of
Displaying Disk Information
Our mission was to employ get-wmiobject to display disk information.
By using 3 or 4 examples, I hope that you gain perspective of the command.
My greatest joy would be if you would amend one of my scripts to suit your
circumstances.
If you like this page then please share it with your friends
See more PowerShell share examples including WMI
•
PowerShell WMI •
Win32_Share •
WMI Shares •
Query
• Get-Acl •
PowerShell Error Codes •
Win32_ComputerSystem
Please email me if you have a example scripts. Also please report any factual mistakes, grammatical errors or broken links, I will be happy to correct the fault.
Download my ebook:
Getting Started with PowerShell - only $9.25
You get 36 topics organized into these 3 sections:
1) Getting Started
2) Real-life tasks
3) Examples of Syntax.
In addition to the ebook, you get a PDF version of this Introduction to PowerShell ebook It runs to 120
pages of A4.
| 
