Introduction to PowerShell

Examples

• 7

  Allow scripts stored on your machine to run un-signed

  edit move example delete share

  7

  By default PowerShell is set up, for security reasons, to only allow signed scripts to execute. Executing the following command will allow you to run unsigned scripts (you must run PowerShell as Administrator to do this).

  Set-ExecutionPolicy RemoteSigned
  

  Another way to run PowerShell scripts is to use Bypass as ExecutionPolicy:

  powershell.exe -ExecutionPolicy Bypass -File "c:\MyScript.ps1"
  

  Temporary work-around for execution policy can be achieved by running the Powershell executable and passing any valid policy as -ExecutionPolicy parameter. The policy is in effect only during process' lifetime, so no administrative access to the registry is needed.

  C:\>powershell -ExecutionPolicy RemoteSigned
  

  There are multiple other policies avaialable, and sites online often encourage you to use Set-ExecutionPolicy Unrestricted. This policy stays in place until changed, and lowers the system security stance. This is not advisable. Use of RemoteSigned is recommended, because it allows locally stored and written code, and requires remotely acquired code be signed with certificate from a trusted root.

  TechNet Documentation:
  Set-ExecutionPolicy
  about_Execution_Policies

  edited Oct 7 at 15:20

  

  

  

  

  

  +3
• 4

  Hello World

  edit move example delete share

  4

  In PowerShell there are many ways to achieve the same result, this can be illustrated nicely with the simple, familiar Hello World example:

  Using Write-Host cmdlet

  Write-Host "Hello World"  
  

  Using Write-Output cmdlet

  Write-Output "Hello world"
  

  Using Aliases like echo

  echo "Hello world"
  

  Or, simply, typing "Hello world"

  "Hello world"
  

  All of which will result with the expected console output

  Hello World
  

  It's worth noting however that while these all achieve the goal "write to screen", Write-Host and Write-Output differ in that the former prints only to stdout (i.e. the console screen) whereas the latter can be can be captured in a variable or pipeline.

  echo and write are aliases for Write-Output.

  edited Aug 1 at 13:39

  

  

  

  
• 2

  The Pipeline - Using Output from a PowerShell cmdlet

  edit move example delete share

  2

  One of the first questions people have when they begin to use PowerShell for scripting is how to manipulate the output from a cmdlet to perform another action.

  The pipeline symbol | is used at the end of a cmdlet to take the data it exports and feed it to the next cmdlet. A simple example is using Select-Object to only show the Name property of a file shown from Get-ChildItem:

  Get-ChildItem | Select-Object Name
  #This may be shortened to:
  gci | Select Name
  

  More advanced usage of the pipeline allows us to pipe the output of a cmdlet into a foreach loop:

  Get-ChildItem | ForEach-Object {
      Copy-Item -Path $_.FullName -destination C:\NewDirectory\ 
  }
  

  Note that the example above uses the $_ symbol - when objects from the pipeline aren't specifically named using | foreach($item in $items) for example, they use this variable.

  edited Jul 22 at 1:01

  

  
• 1

  Installation or Setup

  edit move example delete share

  1

  Windows

  PowerShell is included with the Windows Management Framework. Installation and Setup are not required on modern versions of Windows.

  Updates to PowerShell can be accomplished by installing a newer version of the Windows Management Framework.

  Other Platforms

  "Alpah" version of PowerShell 6 can be installed on other platforms. The installation packages are available here.

  For example, to install on Ubuntu 16.04, download powershell_6.0.0-alpha.9-1ubuntu1.16.04.1_amd64.deb from the releases page onto the Ubuntu machine.

  Run this on terminal:

  sudo apt-get install libunwind8 libicu55
  sudo dpkg -i powershell_6.0.0-alpha.9-1ubuntu1.16.04.1_amd64.deb
  

  Then just run powershell

  edited Sep 5 at 20:43

  

  

  

  
• 0

  Calling .Net Library Methods

  edit move example delete share

  0

  Static .Net library methods can be called from PowerShell by encapsulating the full class name in third bracket and then calling the method using ::

  #calling Path.GetFileName()
  C:\> [System.IO.Path]::GetFileName('C:\Windows\explorer.exe')
  explorer.exe
  

  Static methods can be called from the class itself, but calling non-static methods requires an instance of the .Net class (an object).

  For example, the AddHours method cannot be called from the System.DateTime class itself. It requires an instance of the class :

  C:\> [System.DateTime]::AddHours(15)
  Method invocation failed because [System.DateTime] does not contain a method named 'AddHours'.
  At line:1 char:1
  + [System.DateTime]::AddHours(15)
  + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
      + FullyQualifiedErrorId : MethodNotFound
  

  In this case, we first create an object, for example :

  C:\> $Object = [System.DateTime]::Now
  

  Then, we can use methods of that object, even methods which cannot be called directly from the System.DateTime class, like the AddHours method :

  C:\> $Object.AddHours(15)
  
  Monday 12 September 2016 01:51:19
  

  edited Sep 11 at 12:44

  

  
• 0

  Commenting

  edit move example delete share

  0

  To comment on power scripts by prepending the line using the # (hash) symbol

  # this is a comment in powershell
  Get-ChildItem
  

  created Aug 1 at 13:35

  
• 0

  Creating Objects

  edit move example delete share

  0

  To create object New-Object cmdlet is used

  # this creates a DateTime object and keeps its reference in variable called "var"
  $var = New-Object System.DateTime
  
  #calling constructor with parameters
  $sr = New-Object System.IO.StreamReader -ArgumentList "file path"
  

  In many instances, a new object will be created in order to export data or pass it to another commandlet. This can be done like so:

  $newObject = New-Object -TypeName PSObject -Property @{
      ComputerName = "SERVER1"
      Role = "Interface"
      Environment = "Production"
  }
  

  Instead of storing it in a variable, you could simply pass it out of your command and into the pipeline. You could also add these objects to a collection and then show the results at the end.

  edited Sep 5 at 11:41