PowerShell for Windows Admins

July 7, 2013  2:52 PM


Richard Siddaway Richard Siddaway Profile: Richard Siddaway

One cmdlet that I don’t think gets used enough is Measure-Object. This enables you to find the minimum, maximum, sum and average of a set of numbers coming down the pipeline

PS> 1..12 | Measure-Object -Sum -Maximum -Minimum -Average

Count : 12
Average : 6.5
Sum : 78
Maximum : 12
Minimum : 1
Property :

You can also work with properties:

PS> Get-Process | Measure-Object -Property Handles -Sum -Maximum -Minimum -Average

Count : 59
Average : 481.101694915254
Sum : 28385
Maximum : 2734
Minimum : 0
Property : Handles

You don’t need to select all of the options.

PS> (Get-Process | Measure-Object -Property Handles -Average).Average

Next time you need to find the maximum, minimum, average or sum remember measure-object instead of spending time writing your own routines

July 7, 2013  1:01 PM

Deleting a file with WMI

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

Following on from the last post this is how you can delete a file.

Use the same file structure as previously

This time you need to use the CIM_DataFile class. It’s one of the few classes I’ve found that doesn’t have a Win32_ equivalent.

The class has a Delete method. Assuming you know the full path to the file

Get-CimInstance -ClassName CIM_DataFile -Filter “Name=’C:\\Expendable\\Target1\\proc.txt’ ” |
Invoke-CimMethod -MethodName Delete

You can perform most actions on files and folders using WMI but you can’t create a file or a folder

July 7, 2013  12:41 PM

Deleting Folders with WMI

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

I recently saw a question about deleting folders with WMI.

Let’s create a file structure we’re happy to delete

New-Item -Path c:\ -Name Expendable -ItemType Directory
New-Item -Path c:\Expendable -Name Target1 -ItemType Directory
New-Item -Path c:\Expendable -Name Target2 -ItemType Directory

Get-Process | Out-File -FilePath c:\Expendable\Target1\proc.txt
Get-Service | Out-File -FilePath c:\Expendable\Target2\serv.txt

A look through the WMI classes brings out Win32_Directory

PS> $class = Get-CimClass -ClassName Win32_Directory
PS> $class.CimClassMethods | ft -a

Name ReturnType Parameters
—- ———- ———-
TakeOwnerShip UInt32 {}
ChangeSecurityPermissions UInt32 {Option, SecurityDescriptor}
Copy UInt32 {FileName}
Rename UInt32 {FileName}
Delete UInt32 {}
Compress UInt32 {}
Uncompress UInt32 {}
TakeOwnerShipEx UInt32 {Recursive, StartFileName, StopFileName}
ChangeSecurityPermissionsEx UInt32 {Option, Recursive, SecurityDescriptor,…}
CopyEx UInt32 {FileName, Recursive, StartFileName, StopFileName}
DeleteEx UInt32 {StartFileName, StopFileName}
CompressEx UInt32 {Recursive, StartFileName, StopFileName}
UncompressEx UInt32 {Recursive, StartFileName, StopFileName}
GetEffectivePermission Boolean {Permissions}

The Delete method looks promising

CIM uses inert objects so we need to get an instance an pipe it into Invoke-CimMethod

Get-CimInstance -ClassName Win32_Directory -Filter “Name=’C:\\Expendable'” |
Invoke-CimMethod -MethodName Delete

When you delete a folder like this – the folder, its contents, any subfolders and their contents are deleted. They don’t appear in the recycle bin either so its a one way trip

July 5, 2013  12:56 PM

Excel–named range

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

To create a named range in an Excel spreadsheet

$xl = New-Object -ComObject ‘Excel.Application’
$wkbk = $xl.Workbooks.Add()
$sheet = $wkbk.WorkSheets.Item(1)
$range = $xl.Range(“A1”, “D4”)
$range.Name = “Test”

Just to show how to work with named ranges

$range2 = $xl.Range(“Test”)
$xl.visible = $true

July 4, 2013  12:14 PM

PowerShell help RSS feed

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

The updatable help in PowerShell 3.0 caused a lot of confusion when that version first shipped. The help files have been updated periodically since 3.o shipped but its always been difficult finding out when they’ve been updated.

That’s changed

There is now an RSS feed that provides information on updates to the help files. Written by the team that creates the PowerShell help files you can now keep up to date with changes.

Subscribe at http://sxp.microsoft.com/feeds/msdntn/PowerShellHelpVersions.

July 3, 2013  2:12 PM

Office365 ate my RSS feeds

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

Just been puzzling out why I haven’t been getting any RSS feeds for a few days. Looks like when I hooked up my Office365 account to Outlook it took out all the RSS feeds. Fun time to come putting them back

July 2, 2013  12:58 PM

New-mailbox oddity

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

I’ve been doing a lot with Exchange recently and found an interesting quirk.

If you use the New-mailbox cmdlet with the –PrimarySMTPaddress parameter the mailbox doesn’t get email address policies applied.

You need to use set-mailbox to turn policy application on – after the mailbox has finished creating

June 30, 2013  3:57 PM

Need for speed?

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

How fast does an admin script have to be?

My opinion has always been that if its significantly faster than me doing the same task by hand then that’s more than fast enough.

Is my time better spent developing new functionality compared to shaving a few % off the execution time of my scripts? If the script is long running its either because I’m hitting a lot of data or I’m hitting a lot of machines. In both cases the script itself probably isn’t the bottle neck and if its that long an operation I can always run it over night. A mass mailbox migration may run over a long weekend!

Speed is relative and as long the script delivers its results in an acceptable time frame the absolute time doesn’t really matter.

June 30, 2013  1:52 PM

Using localhost

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

When creating functions that accept a computer name as a parameter you will often see this syntax

param (
[string]$computername = ‘localhost’

This is designed to give a default value in the event of a value not being passed. That’s a good idea if there is a sensible, safe, value you can use and you aren’t making the parameter mandatory.

The only objection I have is to using ‘localhost’

I have seen this break down – for instance if you try to use the System.DirectoryServices.AccountManagement classes against accounts on the local machine. On the other hand you have to use it when dealing with the WSMAN provider.

Just be aware that ‘localhost’ can cause issues

June 28, 2013  11:39 AM

Refreshing values

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

The CIM cmdlets in PowerShell v3 enable you to refresh the data in the object. Try this:

$p = Get-CimInstance -ClassName Win32_PerfFormattedData_PerfOS_Processor
$p | Get-CimInstance | select percentprocessortime

$p will remain unchanged. Another use for this is monitoring processes – you could check on CPU utilisation

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