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Introduction to PowerShell (Move over Bash)

By , 12 Apr 2011
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Introduction

For years, UNIX/Linux administrators have looked down on the Windows environment, one of the main reasons being that Windows did not have a nice CLI. UNIX has always had sh, bash, ksh which are great shells. Microsoft has now introduced Windows PowerShell (codename MONAD), a very powerful .NET based shell. A shell is a great tool for system administrators to automate tasks. PowerShell has all the same features as the current UNIX shells, like:

  • Composition - Which is the combining of many little commands in order to create a complex function
  • Pipes - Being able to pipe information from one command to the next

There are also a few features that set it apart from the other shell environments available on the nix* systems:

  • Object Oriented - PowerShell is fully object oriented. This is one of my favourites, and why I think it is so much more powerful than bash. E.g., in bash, you have the ability to pipe a list of processes to another application. With this list of text, I can then search through it and find some process IDs which match a certain string. However in PowerShell, I get back a list of process objects, objects which have properties and methods.
  • Access to the full .NET 2.0 assemblies - Need I say more?
  • Extensibility - Create you own cmdlet assemblies, so people can script your application. Exchange 2007 is one of the first Windows applications to support PowerShell. Through PowerShell cmdlets, you can run scripts that will manage and automate the administration of exchange. For example, (PS> get-mailbox *noob* | set-mailbox -SendStorageQuota 1GB) would set the quoter for all names that had the string noob in their name.
  • Hosting - Ability to host PowerShell in your .NET application in less than 10 lines of code. Because PowerShell is object oriented, you are able to pass objects from the hosting program into the script, in one line of code.
  • Ability to use Windows COM objects.
  • Strong XML support.

So let's get into it then...

  1. Start by getting the .NET 2.0 runtime from here: .NET Runtime download
  2. Then get PowerShell from here: Download PowerShell
  3. Next we need an IDE (this tool is pure gold for learning PowerShell and writing scripts): http://www.karlprosser.com/coder/?page_id=14

Before we can use the IDE, we need to enable all scripts to be executed. So from PowerShell (Start->Windows PowerShell->Windows PowerShell), we enable scripting.

PS > Get-Help Set-ExecutionPolicy - detailed

This will give us some information regarding Set-ExecutionPolicy Command.

PS > Set-ExecutionPolicy Unrestricted

Lets you run scripts from external sources.

P.S. It is made up of many cmdlets which are DLLs that get interpreted by PS. In the future, we can see how to create our own cmdlets so people can control our applications. For now, let's throw around some built in cmdlets:

Some samples

PS > get-service | get-member

Here the get-service cmdlet is piping a list of service objects to another cmdlet. Get-member is then listing all the available members in the "System.ServiceProcess.ServiceController" class.

PS > get-service schedule | format-list -property *

Here, the get-service is getting the service object 'schedule' and piping it to another cmdlet which formats the output of the properties. There are other formats available, try...

PS > get-service | Format-List

PS > get-service | Format-Custom

PS > get-service | Format-Table

PS > get-service | Format-Wide

PS > get-service | format-table name, Servicetype, Canshutdown

Here we are piping information from ipconfig and filtering with the findstr command.

PS > ipconfig | findstr "Address"

Please note: ipconfig is a command that returns text so it is not returning objects with properties and functions.

Get-Help

There is a large amount of documentation with PS. Get-Help is much like the man command for nix.

Other options:

PS > Get-help get-command -detailed

PS > Get-help get-command -full

PS > Get-help get-command -examples

PS > Get-help get-command -parameter *

Common commands

PS > Get-Command - Gets basic information about cmdlets and about other elements
                   of Windows PowerShell commands.

PS > Get-Process - Gets the processes that are running on the local computer.

PS > Get-Service - Gets the services on the local computer

PS > Get-Eventlog - Gets information about local event logs or the entries stored in
                    those event logs.

PS > Start-transcript, stop-transcript - Lets you record sessions/interaction with PS 

Alias (get-alias)

Alias's are literally command alias's. E.g.: 'ps' is an alias for get-process.

PS > get-alias ps

PS > get-alias | where-object {$_.definition -eq "set-location"}

PS > set-alias gh get-help

PS > set-alias np c:\windows\notepad.exe

PS > remove-item alias:ls

Variables, loops, and string manipulation

Being a scripting language, PS has support for variables, loops, and string manipulation.

Put the results into a variable:

$result = ipconfig

Using a for loop to print out with line numbers..

for ($i=0 ; $i -lt $result.length; $i++ ) 
{
    "{0} {1}" -f $i, $result[$i] 
}

Using foreach...

$i = 1;

foreach($singleLine in $result)
{
    $i++
    "{0}    {1}" -f $i, $singleLine
}

Using built-in string functions...

PS > "How dooz is this".split()

Functions

Functions can be created as with any scripting language. Arguments can be passed and values returned.

$result = ipconfig

function AddLineNumbers
{
    $i = 1;

    foreach($singleLine in $args[0])
    {
        $i++
        "{0}    {1}" -f $i, $singleLine
    }
}

AddLineNumbers $result

WMI (Windows Management Instrumentation) scripting

WMI is an essential technology for Windows administration. WMI gives you access to a huge amount of information for Windows systems. The Get-WmiObject cmdlet provides access to WMI objects.

For example, here we are using Get-WmiObject to get the OS and BIOS information.

Get-WmiObject win32_bios -computername 127.0.0.1
Get-WmiObject -Class Win32_OperatingSystem -ComputerName 127.0.0.1

.NET scripting

A common thing that you would do in scripting is send emails. First, we would need to create a mail message .NET object using New-Object.

PS> $mailMsg = New-Object -TypeName System.Net.Mail.MailMessage(
    " sender@net.com.au"," recipient@net.com.au");

Then we can set some options and the email message.

PS> $mailMsg.IsBodyHtml = $true;

PS> $mailMsg.Body = "<html>This is a sample mail message sent from PowerShell</html>";

PS> $mailMsg.Subject = "This is a sample mail message sent from PowerShell";

Once we have created the mail message, we then need to create the client object and send the email.

PS> $client = New-Object -TypeName System.Net.Mail.SmtpClient("mail.optusnet.com.au");
PS> $client.Send($mailMsg);

Shell profile

All aliases, functions, and variables are only added to the current session. In order to keep changes, you need to add them to your profile. Here is a list of profile locations:

%windir%\system32\WindowsPowerShell\v1.0\profile.ps1

This profile applies to all users and all shells.

%windir%\system32\WindowsPowerShell\v1.0\ Microsoft.PowerShell_profile.ps1

This profile applies to all users, but only to the Microsoft.PowerShell shell.

%UserProfile%\My Documents\WindowsPowerShell\profile.ps1

This profile applies only to the to the current user, but affects all shells.

%UserProfile%\\My Documents\WindowsPowerShell\Microsoft.PowerShell_profile.ps1

This profile applies only to the current user and the Microsoft.PowerShell shell.

You can also create, share, and distribute profiles.

Navigation

PS allows for navigation of the file system, Registry, and certificates on the computer using a common method. To view the available navigation areas, use:

get-psdrive

File system

As per normal.

Registry

cd HKLM:

ls

cd system\currentcontrolset\control

Further reading

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Michael Ridland
Web Developer http://www.thinksmartdigital.com.au
Australia Australia
Michael has been hacking the web since he was a teenage at school. At 17 he started the online magazine ‘The Computer Information Network’. He has a Bachelor of Computer Science with Distinction from the University of Wollongong, completing his degree in the top 10% of the University. He is a member of the Golden Key International Honour Society for his academic achievements.
 
Currently Michael is running Competition Runner a Facebook Contest Software which allows anyone to easily create a photo contest. Michael has consulted to a range of different companies across Australia and the UK such as Unilever, Happen Business, Vodafone UK, Ogilvy & Mather, Flora and uswitch.com. He has consulted as a senior engineer on multi-million dollar projects and worked in teams of 30+ developers.
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Comments and Discussions

 
GeneralMy vote of 4 PinmemberCoding 10119-Apr-11 6:57 
QuestionPowerShell IDE? PinmemberR. Hoffmann19-Apr-11 6:50 
AnswerRe: PowerShell IDE? PinmemberTerranceSmith20-Apr-11 2:57 
GeneralMy vote of 4 PinmemberGlobX18-Apr-11 20:01 

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