In this tutorial the basics of Windows PowerShell is explained with examples.

Only read this article if you need a fast going-through Windows PowerShell basics and if you don’t have time to read the great tutorial by Jesse Hamrick on PowerShell Pro which this article is mostly based on.

This article is mostly useful from those whom have some programing knowledge. I’m not going to explain basic programing concepts.

Contents

Introduction

PowerShell Commands – Cmdlet

PowerShell Aliases

PowerShell Parameters, Objects, and Formatting

Windows PowerShell Provides

Variables, Arrays, Hash Tables

Function and Filters

Conditional Logic

Conditional Logic Loops

PowerShell Scripting

More Exercises

Useful links

Introduction

Windows PowerShell is the Microsoft’s new command console and scripting language. Windows PowerShell is Microsoft’s task automation framework, consisting of a command-line shell and associated scripting language built on top of .NET Framework. PowerShell provides full access to COM and WMI, enabling administrators to perform administrative tasks on both local and remote Windows systems.

PowerShell has power, depth and flexibility and you can research for yourself, with PowerShell you can create new objects for example, Windows Services File system, DirectoryEntry or the simpler, and .Net Framework based object using fully qualified name like System.DateTime.

PowerShell Features

• Cmdlets for performing common system administration tasks, such as managing the registry, services, processes, and event logs, and using Windows Management Instrumentation (WMI).
• A task-based scripting language and support for existing scripts and command-line tools.
• Consistent design. Because cmdlets and system data stores use common syntax and naming conventions, data can be shared easily and the output from one cmdlet can be used as the input to another cmdlet without reformatting or manipulation.
• Simplified, command-based navigation of the operating system, which lets users navigate the registry and other data stores by using the same techniques that they use to navigate the file system.
• Powerful object manipulation capabilities. Objects can be directly manipulated or sent to other tools or databases.
• Extensible interface. Independent software vendors and enterprise developers can build custom tools and utilities to administer their software.

PowerShell output is always a .NET object. That output could be a System.Diagnostics.Process a object or System.IO.FileInfo object or a System.String object. Basically it could be any .NET object whose assembly is loaded into PowerShell including your own .NET objects.

You can run all your command-line executables from within the PowerShell console; you can even run VBScript scripts and batch files from within the PowerShell console. For instance commands such as: cls, dir, cd, etc. can be used within PowerShell. In general, these console commands are “aliases” to Windows PowerShell cmdlets. PowerShell commands are typically case-insensitive.

For example, cd is just another way to reference the Set-Location cmdlet.

To get the complete list of available aliases run the following command:

Get-Alias

To get all available cmdlets in PowerShell type:

Get-Command

Launch PowerShell

Windows PowerShell is installed by default. You can launch it by search for PowerShell or just navigate to Windows System from start. You can also launch Windows PowerShell from Administrative Tools, Windows PowerShell.

The famous blue PowerShell console will be launched:

You can customize the color from Menu, Properties, Color tab.

For scripting purposes Windows PowerShell ISE is used. Windows PowerShell ISE provides a developer environment which you can navigate through all list of objects, make use of IntelliSense, Debugging tools, and other cool stuff.

You can launch Windows PowerShell ISE from Administrative Tools, Windows PowerShell ISE.

PowerShell Concepts

• PowerShell is object-based not text-based

  Traditional command prompt output is text-based while output in PowerShell is not. It looks like text but it is actually an object. The output of a PowerShell command (the object) can be piped into another command without additional programming.

• 
  PowerShell Commands are customizable
  

  PowerShell provides a method to create your own PowerShell cmdlets.

• 
  PowerShell is a Command line interpreter and a scripting environment
  

Cmdlets

Cmdlets are Windows PowerShell commands, and are roughly equivalent to command-line tools.

e.g.

To get all child folders in a specific folder:

Get-ChildItem C:\Scripts -recurse

The -recurse, tells the Get-ChildItem to recursively retrieve information from the parent folder.

The name of the parameters can be written in a short-form as long as it is distinct among all parameters of a specific Cmdlet. For example recursive parameter for Get-ChildItem can just be written as –r, or –rec if there is any other parameter which starts with “r”.

Get-ChildItem C:\Scripts -r

Get-Help cmdlet

PowerShell includes a very extensive help system. Use the command Get-Help followed by the command you want to get help on that.

e.g.

Get-Help Format-List

By adding more after the pipeline you can view the result in paging mode:

Get-Help Format-List –full | more

Pipelining

Pipelining is the term for feeding one command’s output into another command. This allows the second command to act on the input it has received. To pipeline two commands (or cmdlets), simply separate them with the pipe symbol (|).

PowerShell Commands – Cmdlet

There are four categories of PowerShell commands:

• Cmdlet (Command-Let)
• PowerShell Functions
• PowerShell Scripts, and
• native Windows commands.

PowerShell commands have been standardized using a “verb-noun” naming convention know as a cmdlet.

To see a list of cmdlets available in PowerShell type the following cmdlet:

get-command

You can filter the commands based on specific verb or noun.

Get-Command -Verb Get

Get-Command -Noun Service

Note that the PowerShell command line is not case-sensitive.

PowerShell Aliases

Aliasing in PowerShell allows for the use of commands we become accustomed to. Windows users can utilize commands like dir, move, type, cls, etc… PowerShell also provides a set of aliases for Linux; ls, pwd, mv, man, cat, etc… PowerShell Aliases are provided for the purpose of allowing new users the ability to quickly interact with the shell.

An alias is an alternative name assigned to a cmdlet. For example, “dir” is an alias for “Get-ChildItem.”

There are two types of aliases:

• Built-in Aliases – Predefined alternative names for Windows, Unix, and PowerShell cmdlets.
• User-defined Aliases – Custom alternative names created by the user.

You can get the list of built-in aliases by typing the following command:

Get-Alias

For Example, there are three aliases for Get-ChildItem:

• dir
• ls
• gci
• Get-ChildItem

User-Define PowerShell Aliases

User-defined aliases only last while the PowerShell session is active.

To create a user-define alias use the following command:

Set-Alias [alias name] [command name]

e.g.

Create an alias for Get_Service cmdlet

Set-Alias gs Get-Service

There are options to create permanent aliases in PowerShell:

• Import/Export the PowerShell alias.
• User-defined Aliases using PowerShell Profiles.

PowerShell Parameters, Objects, and Formatting

Common Parameters

There are several standard parameters in PowerShell which interpreted by the PowerShell engine. Not all cmdlets use these parameters.

• -whatif – Cmdlet is not actually executed, provides information about “what would happen” if executed.
• -confirm – Prompt user before executing cmdlet.
• -erbose – Provides more detail.
• -debug – Provides debugging information.
• -ErrorAction – Instructs cmdlet to perform an action when errors occur. Such as: continue, stop, silently continue, and inquire.
• -ErrorVariable – Use a specific variable to hold error information. This is in addition to the standard $error variable.
• -OutVariable – Variable used to hold output information.
• -OutBuffer – Hold a certain number of objects before calling the next cmdlet in the pipeline.

Example:

Objects

PowerShell is object-based not text-based. Since we are working with objects, more information exists than what’s presented (by default) on the command line. That information may not be initially visible; by using PowerShell cmdlets, parameters, and script blocks we can interact with an object to provide us with the information we require.

An “Object” is something we can gather information from and/or perform an action upon. An object, in PowerShell, consists of properties (information we can gather) and methods (actions we can perform).

Get-Member

cmdlet

It is used to examine what properties and methods are available to an object.

Example 1

The output of Get-Service is piped into Get-Member

You can filter the search. For instance to only display the properties.

Example 2

To get all files in a folder where write to the disc on specific time.

By executing Get-ChildItem | Get-Member you can see there are two sets of members: System.IO.FileInfo and System.IO.DirectoryInfo. LastWriteTime property will return datetime when the file has written.

Get-ChildItem | Where-Object {$_.LastWriteTime -gt "10/25/2013"}

Formatting

When we execute a cmdlet we are relying on PowerShell to display results. The “Format-” cmdlets allow us to choose which format to display results in. To get a list of formatting options, type the following command:

Get-Command Format-*

Example:

Get-ChildItem -Recurse | Where-Object {$_.LastWriteTime -gt "10/25/2013"} | Format-List

To only shows specific properties:

Get-ChildItem -Recurse | Where-Object {$_.LastWriteTime -gt "10/25/2013"} | Format-List -Property LastWriteTime, FullName, CreationTime

Group-Object

ConvetTo-Html

It will convert the object into HTML which can then be exported to a file.

Get-Process | Sort-Object -Property CPU -Descending | ConvertTo-Html | Out-File "Process.html"

Export-CSV

Export the result to comma separated format.

Get-Process | Export-CSV Processes.csv

Windows PowerShell Provides

PowerShell Providers are .NET programs that allow us to work with data stores as if they were mounted drives. This simplifies accessing external data outside the PowerShell environment. For example, we can access the registry as if it were a file system. This translates to being able to use the same cmdlets as working with files and folders, which are shown in the table below.

A Provider is also called a “snap-in” which is a dynamic link library (.dll) built into PowerShell. A library is code that instructs PowerShell to preform an action when we execute a command.

Execute the following cmdlet to get all available PowerShell providers:

Get-PSProvider

PowerShell Drive

We connect to PowerShell Providers by mounting the Providers PowerShell Drive(PSDrive). Most Providers have only one PSDrive, the exceptions are the FileSystem Provider(depends on the number of drives on the system) and the Registry Provider(HKLM and HKCU).

Get-PSDrive

We connect to each Provider using the PSDrive appended with a colon (:).

Alias Provider

To mount the Alias provider execute the following command:

Set-Location Alias:

Example 1:

Example 2:

Environment Provider

Examples

Create New Variable

-Path . refers to the current location

To Rename a Variable

Rename-Item -Path Env:MyVariable -NewName MyRenamedVar

To Remove a Variable

Remove-Item MyRenamedVar

File System Provider

When PowerShell launched this provider is accessed by default.

To force the PowerShell displays the hidden file and folder:

Get-ChildItem –Force

Examples

Create New Item

Function Provider

To get individual function’s code use Get-Content cmdlet.

Registry Provider

he Registry Provider allows us to connect to two PSDrives; HKCU and HKLM. With the Registry Provider we can:

• Navigate the registry.
• Search the registry.
• Create new registry keys.
• Delete registry keys.
• Add new values.
• Modify existing values.
• Manage ACLs (Access Control Lists).

Connecting to registry

Connect to HKLM

Connect directly to a path

Variable Provider

To use these variables you need to add $ at the beginning.

Variables, Arrays, Hash Tables

• Variables – allows us to store single bits of information.
• Arrays – allows us to store information in an index.
• Hash Table – allows us to store in key-value pairs.

Variables

In PowerShell, variables can contain text strings, integers, and even objects (complete with properties and methods). Special variables exist, which are pre-defined within PowerShell.

Special Variable Examples

• $_ – Contains the current pipeline object, used in script blocks, filters, and the where statement.
• $Args – Contains an array of the parameters passed to a function.
• $Error – Contains objects for which an error occurred while being processed in a cmdlet.
• $Home – Specifies the user’s home directory.
• $PsHome – The directory where the Windows PowerShell is installed.

Example 1: String manipulation

$strMessage = "Today is a very hot day"
Write-Host $strMessage

$strNewMessage = $strMessage -replace "hot", "cold"
Write-Host $strNewMessage

Assigning datatype to variables

[int]$age = 30
[string]$name = "Behnam"
[decimal]$money = 4.5

Write-Host "$name is $age years old and have $money k salary"

Array

One of the more popular uses of an array is to run a script against remote computers. To create an array, we create a variable and assign the array. Arrays are noted by the “@” symbol.

e.g.

$arrMachine = @("Machine1", "Machine2", "Machine3")

Hash Table

A Hash table is also known as a dictionary. It is an array that allows you to store data in a “key-value” pair association. The “key” and “value” entries can be any data type and length.

You should use @ to declare a hash table followed by curly braces. Elements inside the hash table should be separated by a semicolon.

e.g.

$hashEmployees = @{"Behnam" = 1324; "Naser" = 2345; "Disorian" = 9889}

Function and Filters

Functions

A function allows you to name a block of code. The code block can then be called (by its name) once or multiple times anywhere from within your script.

Syntax

Function [FunctionName]
(parameters) {script block}

Example 1: Simple funciton

func_add.ps1

Function Add($x, $y)
{
$add = $x + $y;
Write-Host "The sum is $add"
}

Add 4 5

Example 2: using param keyword

Using param keyword

func_param.ps1

Function Add
{
param($x, $y)

$add = $x + $y;
Write-Host "The sum is $add"
}

Add 4 5

Example 3: using $Args variable

func_args.ps1

Function Parler
{
"I know how to speek $Args"
}

Parler "English" "French" "Russian" "Persian"

Example 4: using $Args elements

func_argsindex

Function Add
{
$Args[0] + $Args[1]
}

Add 5 6

Using $input variable

The $input variable allows a function to access data coming from the pipeline.

Example:

Conditional Logic

Comparison operators

While comparing strings you can add “i” to ignore the case or “c” to consider the case to -eq while comparing (i.e. –ieq and -ceq).

Logical Operations

Conditional Logic

There are two Conditional Logic in PowerShell

• if statement

  Syntax

if (condition) {code block}
elseif (condition) {code block}
else (condition) {code block}

• switch statement

  Syntax

switch (expression)
{
	(test) {code block}
		value {code block}
		default {code block}
}

Example 1: if statement

lgc_if.p1

$x = 4

if ($x -eq 5) {
Write-Host "x is equal to 5"
}
elseif ($x -eq 4) {
Write-Host "x is equal to 4"
}
elseif ($x -eq 3) {
Write-Host "x is equal to 3"
}
else {
Write-Host "I've got no idea what x is!"
}

Example 2: Determining machine’s OS

log_if2.ps1

#$strComputer = Read-Host "Enter Computer Name"
$objWMI = Get-WmiObject -Class win32_ComputerSystem -Namespace "root\CIMV2"
$OS = Get-WmiObject -Class win32_OperatingSystem -Namespace "root\CIMV2" -ComputerName $objWMI.Name

# check if the OS version is Windows XP or Server 2003
if ($OS.Version -eq "5.1.2600") {
Write-Host "OS is Windows XP"
}
elseif ($OS.Version -eq "5.2.3790") {
Write-Host "OS is Windows Server 2003"
}
elseif($OS.Version -eq "6.2.9200") {
Write-Host "OS is Windows 8"
}
else {
Write-Host "Cannot identify your OS!"
}

Output

Example 3: Switch statement

Lgc_switch.ps1

$objWMI = Get-WmiObject -Class win32_ComputerSystem -Namespace "root\CIMV2"

Write-Host "Computer" $objWMI.Name "is a:"

switch($objWMI.DomainRole) {
0 {
Write-Host "Stand alone workstation"
}

1 {
Write-Host "Member workstation"
}

2 {
Write-Host "Stand alone server"
}

3 {
Write-Host "Member server"
}

4 {
Write-Host "Back-up domain controller"
}

5 {
Write-Host "Primary domain controller"
}

default {
Write-Host "The role can not be determined"
}
}

Output

Conditional Logic Loops

Loops

PowerShell provides the following loops:

• do while
• while
• do until
• for
• foreach

break and continue can be use to alter the execution on the loop.

Example 1: While

Count from 1 to 5

Note: You can modify the script in Windows PowerShell ISE

Loop_dowhile.ps1

Using DoWhile

$count = 1

do {
Write-Host $count
$count++
}while($count -le 5)

Using while:

$count = 1

while($count -le 5) {
Write-Host $count
$count++
}

Output

Either a carriage return or semicolon is used to separate commands.

Example 2: DoUntil

Get user’s confirmation

Loop_dountil.ps1

$strResponse = "N"
$strMessage = "Are you sure? (Y | N)"

do {
$strResponse = Read-Host $strMessage
} Until($strResponse -eq "Y")

Output

Example 3: For

Loop_for.ps1

for ($i = 1; $i -le 5; $i++) {
Write-Host $i
}

Output

Using array

$nums = @(1,3,6,7,8,9)
$i = 0

for(; $i -le $nums.Length - 1; $i++) {
Write-Host $nums[$i]
}

Output

Example 4: Foreach

Loop_foreach.ps1

$nums = @(1,3,6,7,8,9)

foreach ($num in $nums) {
Write-Host $num
}

Output

Looping through all running processed

foreach ($item in Get-Process) {
if($item.Responding -eq "True") {
Write-Host $item.Name
}
}

PowerShell Scripting

A PowerShell script is a simple text file. The powershell file contains a series of PowerShell commands, with each command appearing on a separate line. For the text file to be treated as a PowerShell script, its filename needs to use the .PS1 extension.

To create and run a script:

• Type the commands in a text editor
• Save the file with .ps1 extension
• Execute the file in PowerShell

e.g.

Get-Process | Sort-Object ID

You might need to modify the Execution Policy to enables the script execution. This is prohibited by default due to security considerations:

Set-ExecutionPolicy -ExecutionPolicy Unrestricted

e.g.

welcome.ps1

$name = "Behnam"
$message = "Welcome"
Write-Host $message $name

Output

More Exercises

Exercise 1

In this exercise we configure the PowerShell Console to open in a customized directory.

1. Right-Click on the PowerShell shortcut and choose Properties.
2. Under the Shortcut tab locate the Start in: text box.
3. Type in the path to the folder created in step 1. C:\MyScripts
4. Click Ok.
5. Launch PowerShell from the desktop shortcut.

Exercise 2

Stopping and Starting Services

Useful links

http://technet.microsoft.com/en-us/library/ee332526.aspx

http://www.powershellpro.com/powershell-tutorial-introduction

http://www.tuicool.com/articles/bA7VB3

http://technet.microsoft.com/en-us/library/dd315258.aspx

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