In the world of Microsoft system administration, it is becoming impossible to avoid PowerShell. If you've never looked at PowerShell before or want a refresher to make sure you understand what is going on, this chapter would be a good place to start. We will cover the following topics:
Determining the installed PowerShell version
Starting a PowerShell session
Simple PowerShell commands
There are many ways to determine which version of PowerShell, if any, is installed on a computer. We will examine how this information is stored in the registry and how to have PowerShell tell you the version.
It's helpful while learning new things to actually follow along on the computer as much as possible. A big part of the learning process is developing "muscle memory", where you get used to typing the commands you see throughout the book. As you do this, it will also help you pay closer attention to the details in the code you see, since the code won't work correctly if you don't get the syntax right.
If you're running at least Windows 7 or Server 2008, you already have PowerShell installed on your machine. Windows XP and Server 2003 can install PowerShell, but it isn't pre-installed as part of the Operating System (OS). To see if PowerShell is installed at all, no matter what OS is running, inspect the following registry entry:
If this exists and contains the value of 1, PowerShell is installed. To see, using the registry, what version of PowerShell is installed, there are a couple of places to look at.
First, the following value will exist if PowerShell 3.0 or higher is installed:
If this registry entry does not exist, you have either PowerShell 1.0 or 2.0 installed. To determine which, examine the following registry entry (note the 3 is changed to 1):
This entry will either contain 1.0 or 2.0, to match the installed version of PowerShell.
It is important to note that all versions of PowerShell after 2.0 include the 2.0 engine, so this registry entry will exist for any version of PowerShell. For example, even if you have PowerShell 5.0 installed, you will also have the PowerShell 2.0 engine installed and will see both 5.0 and 2.0 in the registry.
In this folder, there will be an executable file called
PowerShell.exe. There should be a shortcut to this in your start menu, or in the start screen, depending on your operating system. In either of these, search for PowerShell and you should find it. Running this program opens the PowerShell console, which is present in all the versions.
At first glance, this looks like Command Prompt but the text (and perhaps the color) should give a clue that something is different:
Downloading the example code
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In this console, type
$PSVersionTable in the command-line and press Enter. If the output is an error message, PowerShell 1.0 is installed, because the
$PSVersionTable variable was introduced in PowerShell 2.0. If a table of version information is seen, the PSVersion entry in the table is the installed version. The following is the output on a typical computer, showing that PowerShell 4.0 is installed:
If you don't have PowerShell installed or want a more recent version of PowerShell, you'll need to find the Windows Management Framework (WMF) download that matches the PowerShell version you want. WMF includes PowerShell as well as other related tools such as Windows Remoting (WinRM), Windows Management Instrumentation (WMI), and Desired State Configuration (DSC). The contents of the distribution change from version to version, so make sure to read the release notes included in the download. Here are links to the installers:
5.0 (Feb. Preview)
The PowerShell 1.0 installer was released as an executable (
.exe), but since then the releases have all been as standalone Windows update installers (
.msu). All of these are painless to execute. You can simply download the file and run it from the explorer or from the Run… option in the start menu. PowerShell installs don't typically require a reboot but it's best to plan on doing one, just in case.
It's important to note that you can only have one version of PowerShell installed, and you can't install a lower version than the version that was shipped with your OS. Also, there are noted compatibility issues between various versions of PowerShell and Microsoft products such as Exchange, System Center, and Small Business Server, so make sure to read the system requirements section on the download page. Most of the conflicts can be resolved with a service pack of the software, but you should be sure of this before upgrading PowerShell on a server.
We already started a PowerShell session earlier in the section on using PowerShell to find the installed version. So, what more is there to see? It turns out that there is more than one program used to run PowerShell, possibly more than one version of each of these programs, and finally, more than one way to start each of them. It might sound confusing but it will all make sense shortly.
A PowerShell host is a program that provides access to the PowerShell engine in order to run PowerShell commands and scripts. The
PowerShell.exe that we saw in the
PSHOME directory earlier in this chapter is known as the console host. It is cosmetically similar to Command Prompt (
cmd.exe) and only provides a command-line interface. Starting with Version 2.0 of PowerShell, a second host was provided.
The Integrated Scripting Environment (ISE) is a graphical environment providing multiple editors in a tabbed interface along with menus and the ability to use plugins. While not as fully featured as an Integrated Development Environment (IDE), the ISE is a tremendous productivity tool used to build PowerShell scripts and is a great improvement over using an editor, such as notepad for development.
The ISE executable is stored in
PSHOME, and is named
powershell_ise.exe. In Version 2.0 of the ISE, there were three sections, a tabbed editor, a console for input, and a section for output. Starting with Version 3.0, the input and output sections were combined into a single console that is more similar to the interface of the console host. The Version 4.0 ISE is shown as follows:
I will be using the Light Console, Light Editor theme for the ISE in most of the screenshots for this book, because the dark console does not work well on the printed page. To switch to this theme, open the Options item in the Tools Menu and select Manage Themes... in the options window:
Press the Manage Themes... button, select the Light Console, Light Editor option from the list and press OK. Press OK again to exit the options screen and your ISE should look something similar to the following:
Note that you can customize the appearance of the text in the editor and the console pane in other ways as well. Other than switching to the light console display, I will try to keep the settings to default.
In addition to the console host and the ISE, if you have a 64-bit operating system, you will also have 64-bit and 32-bit PowerShell installations that will include separate copies of both the hosts.
As mentioned before, the main installation directory, or
PSHOME, is found at
%WINDIR%\System32\WindowsPowerShell\v1.0\. The version of PowerShell in
PSHOME matches that of the the operating system. In other words, on a 64-bit OS, the PowerShell in
PSHOME is 64-bit. On a 32-bit system,
PSHOME has a 32-bit PowerShell install. On a 64-bit system, a second 32-bit system is found in
Isn't that backward?
It seems backward that the 64-bit install is in the
System32 folder and the 32-bit install is in
System32 folder is always the primary system directory on a Windows computer, and this name has remained for backward compatibility reasons. SysWOW64 is short for Windows on Windows 64-bit. It contains the 32-bit binaries required for 32-bit programs to run in a 64-bit system, since 32-bit programs can't use the 64-bit binaries in System32.
Looking in the
Program Files\Accessories\Windows PowerShell menu in the start menu of a 64-bit Windows 7 install, we see the following:
Here, the 32-bit hosts are labeled as (x86) and the 64-bit versions are undesignated. When you run the 32-bit hosts on a 64-bit system, you will also see the (x86) designation in the title bar:
When you run a PowerShell host, the session is not elevated. This means that even though you might be an administrator of the machine, the PowerShell session is not running with administrator privileges. This is a safety feature to help prevent users from inadvertently running a script that damages the system.
In order to run a PowerShell session as an administrator, you have a couple of options. First, you can right-click on the shortcut for the host and select Run as administrator from the context menu. When you do this, unless you have disabled the UAC alerts, you will see a User Account Control (UAC) prompt verifying whether you want to allow the application to run as an administrator.
Selecting Yes allows the program to run as an administrator, and the title bar reflects that this is the case:
The second way to run one of the hosts as an administrator is to right-click on the shortcut and choose Properties. On the shortcut tab of the properties window, press the Advanced button. In the Advanced Properties window that pops up, check the Run as administrator checkbox and press OK, and OK again to exit out of the properties window:
Now that we know all the ways that can get a PowerShell session started, what can we do in a PowerShell session? I like to introduce people to PowerShell by pointing out that most of the command-line tools that they already know work fine in PowerShell. For instance, try using
PING. Commands that are part of Command Prompt (think DOS commands) might work slightly different in PowerShell if you look closely, but typical command-line applications work exactly the same as they have always worked in Command Prompt:
By controlling the list of verbs, Microsoft has made it easier to learn PowerShell. The list is not very long and it doesn't contain verbs that have the same meaning (such as Stop, End, Terminate, and Quit), so once you learn a cmdlet using a specific verb, you can easily guess the meaning of the cmdlet names that include the verb.
Some other easy to understand cmdlets are:
Clear-Host(clears the screen)
Get-Date(outputs the date)
Start-Service(starts a service)
Stop-Process(stops a process)
Get-Help(shows help about something)
Note that these use several different verbs. From this list, you can probably guess what cmdlet you would use to stop a service. Since you know there's a
Start-Service cmdlet, and you know from the
Stop-Process cmdlet that Stop is a valid verb, it is logical that
Stop-Service is what you would use. The consistency of PowerShell cmdlet naming is a tremendous benefit to learners of PowerShell, and it is a policy that is important as you write the PowerShell code.
What is a cmdlet?
The term cmdlet was coined by Jeffery Snover, the inventor of PowerShell to refer to the PowerShell commands. The PowerShell commands aren't particularly different from other commands, but by giving a unique name to them, he ensured that PowerShell users would be able to use search engines to easily find PowerShell code simply by including the term cmdlet.
If you tried to use
CD in the last section, you may have noticed that they didn't work exactly as the DOS commands that they resemble. In case you didn't see this, enter
/S on a PowerShell prompt and see what happens. You will either get an error complaining about a path not existing, or get a listing of a directory called
S. Either way, it's not the listing of files including subdirectories. Similarly, you might have noticed that
CD in PowerShell allows you to switch between drives without using the
/D option and even lets you change to a UNC path. The point is that, these are not DOS commands. What you're seeing is a PowerShell alias.
Aliases in PowerShell are alternate names that PowerShell uses for both PowerShell commands and programs. For instance, in PowerShell,
DIR is actually an alias for the
Get-ChildItem cmdlet. The
CD alias points to the
Set-Location cmdlet. Aliases exist for many of the cmdlets that perform operations similar to the commands in DOS, Linux, or Unix shells. Aliases serve two main purposes in PowerShell, as follows:
They allow more concise code on Command Prompt
They ease users' transition from other shells to PowerShell
Here we can see that the
Get-ChildItem cmdlet has three aliases. The first and last assist in transitioning from DOS and Linux shells, and the middle one is an abbreviation using the first letters in the name of the cmdlet.
This chapter focused on figuring out what version of PowerShell was installed and the many ways to start a PowerShell session. A quick introduction to PowerShell cmdlets showed that a lot of the command-line knowledge we have from DOS can be used in PowerShell and that aliases make this transition easier.
In the next chapter, we will look at the
Get-Member cmdlets, and learn how they unlock the entire PowerShell ecosystem for us.
The Monad Manifesto, which outlines the original vision of the PowerShell project: http://blogs.msdn.com/b/powershell/archive/2007/03/19/monad-manifesto-the-origin-of-windows-powershell.aspx
Microsoft's approved cmdlet verb list: http://msdn.microsoft.com/en-us/library/ms714428.aspx
get-help about_ PowerShell_ISE.exe