Getting Started with Powershell: Learn the fundamentals of PowerShell to build reusable scripts and functions to automate administrative tasks with Windows

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:

HKLM\Software\Microsoft\PowerShell\1\Install

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:

HKLM\SOFTWARE\Microsoft\PowerShell\3\PowerShellEngine\PowerShellVersion

If this value exists, it will contain the PowerShell version that is installed. For instance, my Windows 7 computer is running PowerShell 4.0, so regedit.exe shows the value of 4.0 in that entry:

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):

HKLM\SOFTWARE\Microsoft\PowerShell\1\PowerShellEngine\PowerShellVersion

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.

No matter what version of PowerShell you have installed, it will be installed in the same place. This installation directory is called PSHOME and is located at:

%WINDIR%\System32\WindowsPowerShell\v1.0\

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:

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:

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 %WINDIR%\SysWOW64\WindowsPowerShell\v1.0.

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:

Using this technique will cause the shortcut to always launch as an administrator, although the UAC prompt will still appear.