Microsoft SQL Server 2008 R2 Unleashed- P55 pot

Installing PowerShell As of Windows Server 2008, adding the PowerShell feature is easy using the new Server Manager application.. Scriptable and Interactive PowerShell can be used as a s

Provider—Using this PowerShell functionality, a data store is presented to the user

in a format similar to a file system Some of the “core” cmdlets are typically used to

do various tasks such as creating items like files and/or folders

Snap-in—PowerShell functionality can be extended with the use of snap-ins They

are basically DLL files written in a NET programming language such as C# or

VB.NET DBAs can load these snap-ins in their PowerShell session to add additional

functionality such as additional cmdlets and/or providers

Tab completion—This PowerShell functionality allows the user to press the Tab key

to autocomplete supported commands and parameters

Aliases—Theseare shorter names that can be used for cmdlets For example, some

typical UNIX and DOS commands have had aliases for them created in PowerShell

These aliases map to the actual PowerShell cmdlet

Object-Based Functionality

As mentioned earlier, PowerShell is built on the NET Framework This implies that

every-thing within PowerShell is object based This is a familiar concept for anyone who is already

familiar with the NET Framework or NET programming languages such as C# or VB.NET

This object-based functionality is an important concept to remember if you want to dive

deeper into PowerShell PowerShell provides many features, and it can also use additional

features provided by other NET assemblies

SQL Server Management Objects

SQL Server Management Objects (SMO) are a very useful tool to advanced users and

devel-opers when dealing with the automation of SQL Server 2005 and 2008 A lot of the

features within SQL Server (core engine, agent, mail, and so on) are packaged into

easy-to-access NET libraries that can be easy-to-accessed from PowerShell

Most of the functionality provided by the new PowerShell support in SQL 2008 is based

on SMO

As for SQL Server 2005, PowerShell can still be used to administer this version via SMO

The only difference is that the relevant assemblies must be loaded manually

WMI

Windows Management Instrumentation (WMI) is a Windows service that provides remote

control and management PowerShell provides some built-in support for retrieving

infor-mation via WMI

Although the main goal of WMI may be to provide remote access, it can also be used

locally and can provide a wealth of information about a system For example, WMI can be

FIGURE 17.1 Selecting the Windows PowerShell feature

used to easily query disk space and installed patches Examples of using WMI are shown

later in this chapter

Installing PowerShell

As of Windows Server 2008, adding the PowerShell feature is easy using the new Server

Manager application With previous versions of Windows, PowerShell was a separate

install, which required downloading and installing an external package

To install PowerShell on Server 2008, start Server Manager, go to the Features node, then

click Add Features, and simply check the box for Windows PowerShell, as shown in Figure

17.1

PowerShell Console

You can accessing PowerShell directly from the Start menu, by opening All Programs, and

choosing Windows PowerShell 1.0, then finally Windows PowerShell (alternatively, on

some systems, such as Windows 7, you can find the Windows PowerShell folder under the

Accessories folder in the Start menu) The Windows PowerShell console opens, as shown

in Figure 17.2

ptg FIGURE 17.2 Opening the PowerShell console

NOTE

The prompt displayed in examples of the PowerShell console in this chapter has been

changed from the default

Scriptable and Interactive

PowerShell can be used as a scripting language, by creating reusable scripts that can

auto-mate various tasks, and it can also be used interactively, by opening up a console window

and entering commands line by line

In interactive mode, PowerShell is intelligent enough to know when a command is not

complete and actually displays >> on a new line when it believes a complete command

has not been entered

Default Security

After PowerShell has been installed, it is very secure out of the box Here are two of the

default security features:

PowerShell cannot run any scripts If you attempt to double-click on any ps1 script,

it simply opens the contents in Notepad

PowerShell cannot be accessed remotely

Execution Policy

By default, PowerShell can only be used interactively from the console This is part of the

default security To be able to actually run scripts, you must set the execution policy The

easiest way to set this policy is to use the Set-ExecutionPolicy cmdlet, as follows:

PS>Set-ExecutionPolicy RemoteSigned

Basically, when you use the value RemoteSigned, PowerShell is set to be able to run scripts

that have been created locally, but if a script is downloaded from the Internet, for

example, it must be signed

NOTE

The details of the different execution policy settings available or the advantages and

disadvantages of different possibilities are not covered in this chapter Using

RemoteSigned is one of the better trade-offs between functionality and security for

most users

Profiles

As users become more and more familiar with PowerShell, they typically develop

customizations that they may want to save for the next time PowerShell is opened

PowerShell has several profiles that can be used to configure user and system-wide

settings The system-wide profile is easy to access using the following:

PS>notepad $profile

NOTE

On a new install, this file typically doesn’t exist, so don’t be surprised if a window pops

up asking you to create the file Adding commands to the profile is usually as easy as

adding the exact same commands that you would execute in the shell directly into the

profile

Built-in Help Features

As mentioned earlier, cmdlets are the most basic component of PowerShell Three of these

cmdlets are essential in attempting to learn PowerShell Even advanced users may still use

these cmdlets on a daily basis:

Get-Command—This cmdlet is essential in discovering what commands can be used

and what might be available on the system to help with a certain task

Get-Help—When you are looking for additional details, specifically on other

cmdlets, this is the main cmdlet to use

Get-Member—Absolute beginners don’t typically start using this cmdlet when first

initiated into PowerShell, but for advanced users, and easier discovery, this cmdlet is

very useful

Let’s look at each of these cmdlets in more detail

Get-Command

The Get-Command cmdlet can be used to get a listing of an entire list of cmdlets on the

system, but it can also be used to get cmdlets that can be used for a specific task or

purpose For example, Get-Command alone in the console prints the entire list of available

cmdlets available in the current console:

PS>Get-Command

If this is the first time you have ever opened a PowerShell console, how do you write to

the console? How about displaying something as simple as “Welcome to SQL 2008”? You

can pass something basic to Get-Command, such as the string ”*write*”:

PS>Get-Command *write*

What results is a listing of all the cmdlets that have the string ”write” in any part of

their name

In addition, the preceding command also displays any applications and aliases (aliases are

discussed later in this chapter) found in the current user’s path

PowerShell can be pretty smart The preceding sample is actually a shortcut for something

longer like this:

PS>Get-Command -Name *write*

Based on how the cmdlet is programmed, cmdlets can automatically assign a particular

value to a parameter even when the parameter isn’t explicitly typed out

Originally, we were looking for a cmdlet to display something on the console and found

the cmdlet Write-Host Let’s try it:

PS>Write-Host “Welcome to SQL 2008”

Get-Help

The learning curve with PowerShell can be relatively steep Sometimes you can find a

particular command for a particular task, such as the Write-Host cmdlet in the preceding

section, but you might not always be sure how to actually use it Write-Host is simple, but

what if Write-Host had other useful features, or help was required for some other cmdlet?

Get-Help is a very useful cmdlet Just using Get-Help alone provides some default help

information:

PS>Get-Help

To get help on a particular cmdlet, you can use Get-Help and pass the other cmdlet as an

argument:

PS>Get-Help Write-Host

That approach might not provide a lot of useful information; perhaps the –Full and

–Examples parameters are more useful:

PS>Get-Help Write-Host -Full

Passing the –Full parameter gives a detailed description of the cmdlet and all its

parame-ters (including what types of values they accept) If you are a more experienced user, the

–Examples parameter is very useful, because it just gives some examples of using the

cmdlet, which is an easy way to remember the syntax of a particular command:

PS>Get-Help Write-Host -Examples

NOTE

Get-Help works on other cmdlets, but it can also be used when you are looking for

additional details on other concepts in PowerShell To get a listing of the built-in help

for various concepts in PowerShell, you can run the command Get-Help about_*

Get-Member

Because everything in PowerShell is object based, some of the features that can be accessed

are always visible To find out more about a particular object, you can use the Get-Member

cmdlet to look at all its members (the more interesting members of a NET object are

usually its properties and methods)

Using something simple like ”AdventureWorks2008R2”, you can easily look at PowerShell’s

members (possibly without having to consult any NET developer-focused

documenta-tion) ”AdventureWorks2008R2” is a string—in other words, a combination of

alphanu-meric characters (that can include spaces) The following example is another way to

display a string in the PowerShell console:

PS>”AdventureWorks2008R2”

PowerShell automatically recognizes this is a simple string and displays it

A string can be easily displayed to the console, but what else can you do with a string

object? In the NET Framework, a string is really a System.String object The NET

Framework provides a lot of functionality that can be used to deal with strings Now let’s

consider another example:

PS>” AdventureWorks2008R2”|Get-Member

From the preceding command, more information is displayed now, including

TypeName:System.String, which confirms that this is a System.String object One

partic-ular feature that Get-Member indicates is that there is a ToLower method supported by this

particular object:

PS>”AdventureWorks2008R2”.ToLower()

In this example, the ToLower method of the System.String object is used to change the

string into all lowercase letters

PowerShell Scripting Basics

The following sections cover some of the basics of scripting with PowerShell We hope this

information will help you understand how you can use PowerShell in various situations to

automate various tasks

A Few Basic Cmdlets

Following is a list of a few basic cmdlets and how they can be used, with a brief example:

used to list things such as files and directories in a file system Example:

Get-ChildItem *.ps1

Select-Object –Examples for examples

Group-Object –Examples for examples

Sort-Object –Examples for examples

continuing Example: Read-Host “Enter a database name”

took to run Example: Measure-Command {Get-Command}

was covered earlier

are provided later

with no arguments, lists all the aliases configured on the local system

files are supported Example: Get-Content my_script.ps1

Add-Content my_file.txt “testing”

content) Example: Set-Content my_file.txt “testing 123”

the console to a specific text file Example: Start-Transcript

Creating a PowerShell Script

Creating a PowerShell script is as simple as placing a few commands into a ps1 script and

then invoking that script Here’s a simple example of putting the Write-Host cmdlet into

a script and then running it

PS> add-content c:\temp\test.ps1 “Write-Host `testing`”

PS>c:\temp\test.ps1

testing

PS>

In the preceding example, a Write-Host cmdlet was placed in a file named test.ps1, and

then the file was invoked The output resulted in the string ”testing” being output to the

script Notepad or any other simple text editor could also be used to create more

compli-cated scripts

Sample PowerShell scripts that directly apply to SQL Server administration are provided

later in this chapter Refer to the ”The Step-By-Step Examples” section

Adding Comments

Adding comments to a PowerShell script is as simple as adding the # character at the

beginning of the line To comment out entire blocks of code, you must use a # on each

line

NOTE

Another way to comment out blocks of code is to use something called a here string

This technique is not covered in this book

Variables

Strings and objects were discussed earlier in this chapter A very useful feature of

PowerShell, and thus of SQL-PowerShell, is the ability to place objects into a variable This

allows you to run any kind of command and place any objects produced into a variable

for later use

Examples of using variables are presented later in this chapter For now, a string can be

easily saved as a variable:

PS>$var=”AdventureWorks2008R2”

PS>$var

AdventureWorks2008R2

In the preceding example, the string is saved as the variable $var and then output to the

script when the variable is simply invoked:

PS>$database=read-host “Enter a database name”

Enter a database name:AdventureWorks2008R2

PS>$database

AdventureWorks2008R2

The Read-Host cmdlet was introduced briefly already In this example, the Read-Host

cmdlet is used to read input from the console, and the information input is passed to the

$database variable

NOTE

When you perform certain actions in a script, a function, and even from the command

line, the scope assigned to the variable or function determines how this variable will be

seen by other scripts, functions, and so on The details of scoping are not discussed

any further, but it is still an important concept to remember as you use PowerShell

more and more

NOTE

You can issue the Get-Help about_shell_variable and Get-Help about_scope

commands in Powershell for more information and examples about shell variables

An example provided later in this chapter demonstrates that objects much more

compli-cated than simple strings can be saved to a variable for later use

Escaping Characters

Often a special character may be used—for example, in DOS commands—but PowerShell

tries to interpret it differently Let’s consider the dollar sign character ($) PowerShell

normally tries to interpret it as a variable:

PS C:\> $var=”$5 discount”

PS C:\> $var

discount

PS C:\> $var=”`$5 discount”

PS C:\> $var

$5 discount

PS C:\>

The preceding example shows how the escape character, which is the backtick (`), is used

to escape the dollar sign, so that PowerShell doesn’t try to interpret the character literally

as the beginning of a variable

NOTE

You can execute the Get-Help about_escape_character command in PowerShell for

more information and examples

Special Variable $_

In PowerShell, $_ is a special variable that represents the current object in the pipeline

When several cmdlets are piped together, this special variable may be used often Several

examples of using this special variable are shown later in this chapter

NOTE

A special variable named $input also represents objects passed along the pipeline,

but we do not look at this variable in any further detail in this chapter

NOTE

See Get-Help about_automatic_variables for more information and examples

Joining Variables and Strings

The concept of objects was already introduced briefly When you are dealing with simple

strings, you can easily concatenate them together using the plus (+) sign to create a new

string:

PS>$last_name=”Doe”

PS>$first_name=”John”

PS>$full_name=$last_name+”, “+$first_name

PS>$full_name

Doe, John

PS>

In this example, two variables containing simple strings are defined, and they are simply

concatenated together to create a third variable, which is then displayed to the console

NOTE

This kind of concatenation works when both variables are strings An error may be

returned if the variable is of another data type

An example is provided later with the AdventureWorks2008R2 database where string

vari-ables from two different columns in the same table will be joined together using this

feature