Monthly Archives: April 2013

Getting the folder name

Consider the file information from get-childitem

PS> $file = ls servicesv0.6.txt

 

Fullname gives the full path to the file

PS> $file.Fullname
C:\MyData\SkyDrive\Data\scripts\servicesv0.6.txt

 

if you use DirectoryName you get the full path to the parent directory

 

PS> $file.DirectoryName
C:\MyData\SkyDrive\Data\scripts

 

The easiest way to get the folder holding the path is like this

PS> Split-Path -Path $file.DirectoryName -Leaf
scripts

 

However on a Windows 8/PS 3 setup you can also do this

PS> $file.Directory | select -ExpandProperty Name
scripts

Don’t go mad on a one liner

Looking at my first group of entries for Beginners Event 1 I’ve noticed what seems like a fanatical attempt to squash everything onto one line.

command; command; command; command 

is NOT a one liner.  The ; marks the end of a line

command | command | command | command

IS a one liner, even if it goes onto multiple lines!

Don’t think one liner – think one PIPELINE

Read the Question

When my children were at school and going off for a test or exam the last thing I told them was read the question.

It seems this needs to be repeated for the Scripting Games.  The Beginners Event 1 involved MOVING files from one server to another. I have seen a significant number of answers that are COPYING files.

Close doesn’t count in the Scripting Games.

Please read the question before diving into an answer

WMI vs CIM speed tests–the final round

As a final test I want to see what happened when I ran multiple commands against the remote machine.

PS> 1..100 |
foreach {
Measure-Command -Expression{1..100 | foreach {
Get-WmiObject -Class Win32_ComputerSystem -ComputerName W12SUS;
Get-WmiObject -Class Win32_OperatingSystem -ComputerName W12SUS;
Get-WmiObject -Class Win32_LogicalDisk -ComputerName W12SUS}}
} |
Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 6986.797156
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds


PS> 1..100 |
foreach {
Measure-Command -Expression{1..100 | foreach {
Get-CimInstance -ClassName Win32_ComputerSystem -ComputerName W12SUS;
Get-CimInstance -ClassName Win32_OperatingSystem -ComputerName W12SUS;
Get-CimInstance -ClassName Win32_LogicalDisk -ComputerName W12SUS}}
} |
Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 8430.833188
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds

 

PS> $sess = New-CimSession -ComputerName W12SUS
PS> 1..100 |
foreach {
Measure-Command -Expression{1..100 | foreach {
Get-CimInstance -ClassName Win32_ComputerSystem -CimSession $sess;
Get-CimInstance -ClassName Win32_OperatingSystem -CimSession $sess;
Get-CimInstance -ClassName Win32_LogicalDisk -CimSession $sess}}
} |
Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 3460.203938
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds

WMI is slightly faster than CIM but using a CIM session is by far and away the fastest.

My conclusion is that WMI and CIM are comparable, with WMI having a slight edge for speed. If you want to run multiple commands against a remote machine you need to use a CIM session as it is way faster.

Backticks are baaaaaad; don’t do backticks

The voting/judging process has started for event 1 in the 2013 Scripting Games.  What I’m going to be doing over the next few weeks is point out some of the things that I’ve noticed when judging. Some will be good things that I think you should adopt; others will be bad things that you should avoid. There even may be some interesting stuff to get you thinking.

First off is the use of the backtick as a line continuation:

Get-Process | `
sort Handles –Descending

You don’t need a backtick at this point.  The pipe symbol acts as a line continuation marker so the backtick is redundant. All you need to do is this:

Get-Process |
sort Handles -Descending

Its the same with commas. You don’t need to do this:

Get-Process |
select Name, Id, `
Handles, CPU

because it works without the backtick

Get-Process |
select Name, Id,
Handles, CPU

You may see backticks used a lot in books but that is an attempt to reduce the width of the code to make it fit the page. We want you to be able to copy the code from the ebook and run it. The alternative is a line continuation marker which you would have to remove.

Bottom line – 99.9% recurring of the time you don’t need backticks as line continuation markers

CIM vs WMI cmdlets-remote execution speed

Following on from my previous post we’ll look at how the two types of cmdlets compare for accessing remote machines.

I used a similar format to the previous tests but was accessing a remote machine.

First off was the WMI cmdlet – using DCOM to access the remote Windows 2012 server

PS> 1..100 |
foreach {
Measure-Command -Expression{1..100 | foreach {Get-WmiObject -Class Win32_ComputerSystem -ComputerName W12SUS }}
} |
Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 2084.122547
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds

 

The CIM cmdlets are similar but apparently a bit slower – probably due to having to build the WSMAN connection and teat it down each time.


PS> 1..100 |
foreach {
Measure-Command -Expression{1..100 | foreach {Get-CimInstance -ClassName Win32_ComputerSystem -ComputerName W12SUS }}
} |
Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 2627.287458
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds

 

So what happens is you run the CIM command over a CIM session?


PS> $sess = New-CimSession -ComputerName W12SUS
PS> 1..100 |
foreach {
Measure-Command -Expression{1..100 | foreach {Get-CimInstance -ClassName Win32_ComputerSystem -CimSession $sess }}
} |
Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 877.746649999999
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds

This removes the setup and tear-down of the WSMAN connection. It suggests that the actual retrieval time for the CIM cmdlets should be reduced to 1749.540808 milliseconds for 100 accesses which is faster than the WMI cmdlets

It looks like the fastest way to access WMI information is across a CIM session. Next time we’ll look at running multiple commands

AD Management in a Month of Lunches– chapter 9 in MEAP

The MEAP for AD Management in a Month of Lunches has been updated with the release of chapter 9 on managing group policies

CIM cmdlets vs WMI cmdlets–speed of execution

One question that came up at the summit was the comparative speed of execution of the new CIM cmdlets vs the old WMI cmdlets.  No of us knew the answer because we’d never tried measuring the speed.

I decided to perform some tests.

This first test is accessing the local machine.  In both cases the cmdlets are using COM.  WMI uses COM and CIM will use COM if a –ComputerName parameter isn’t used.

The results are as follows:

PS> 1..100 |
foreach {Measure-Command -Expression {
1..100 | foreach {Get-WmiObject -Class Win32_ComputerSystem} }
} | Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 2008.953978
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds

 

PS> 1..100 |
foreach {Measure-Command -Expression {
1..100 | foreach {Get-CimInstance -ClassName Win32_ComputerSystem} }
} | Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 2078.763174
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds

 

So for pure COM access the WMI cmdlets are marginally (3.4%) faster.

What if we use the ComputerName parameter?

PS> 1..100 |
foreach {
Measure-Command -Expression {
1..100 | foreach {Get-WmiObject -Class Win32_ComputerSystem -ComputerName $env:COMPUTERNAME } }
} | Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 1499.14379
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds

PS> 1..100 |
foreach {
Measure-Command -Expression {
1..100 | foreach {Get-CimInstance -ClassName Win32_ComputerSystem -ComputerName $env:COMPUTERNAME } }
} | Measure-Object -Average TotalMilliseconds


Count    : 100
Average  : 3892.921851
Sum      :
Maximum  :
Minimum  :
Property : TotalMilliseconds


This one surprised me – the WMI cmdlets are 2.5 times faster.  I suspect that is because the CIM cmdlet has to build and then breakdown the WSMAN connection each time.

Next time we’ll look at accessing a remote machine.

Time for D-CRUD?

I was thinking on the plane back from the PowerShell summit about the CRUD activities. They are a concept we have inherited from the database world:

C = Create

R = Read

U = Update

D= Delete

Create, Update and Delete correspond directly to the PowerShell verbs – New,Set and Remove respectively.

The Read action corresponds to the Get verb.

Well sort of.

Get-* is used in two distinct scenarios.  Firstly we know of an object and we we want to read its properties – for example:

Get-Process -Name powershell

We are reading the information about the PowerShell process. That corresponds directly to the Read action in the CRUD paradigm.

However, we also use Get* when we want to Discover the processes that are running:

Get-Process

In which case we are Discovering the processes that are running.

I think its time to update the CRUD concept and make it DCRUD where D stands for discovery.

Scripting Games 2013 have started

The 2013 Scripting Games kicked off during the PowerShell summit.  Event 1 is open and you can submit entries up until 23:59:59 GMT on 29 April 2013.  Voting on the entries starts at at midnight on 30 April.

You can enter and you can vote on the entries.  This is a community games run by powershell.org – all are welcome.

If you haven’t entered yet there is still plenty of time to get you entry in for event 1.  Start by reviewing the information at http://powershell.org/wp/the-scripting-games/

Enjoy and good luck