Author Kamal Kumar on August 22, 2020 217  Views

PowerShell for Windows and Linux ~ Chapter 1

PowerShell is Microsoft’s proprietary language to do it’s basic to very advanced level tasks. Things like getting Windows Configuration using WMI, settings up server, configuring Active Directory, scheduling events, manipulating Windows Registry, and much more. PowerShell has a variety of modules like Active Directory, Cirtrix POSH, VMware.PowerCLI, Salesforces, ServiceNow, and many more which make it very vast. In this article, we’ll cover Understanding Scripting languages, differences between Configuration Languages and Scripting languages, etc.
What we will cover in this article -

Introduction to scripting languages, scripting and configuration management languages

Scripting tools are very handy if we want to automate things. There are a variety of tools and languages including -

  • BASH Scripting
  • PowerShell
  • IBM's Job Control Language (JCL)
  • Perl
  • Ruby
  • Python
  • Go scripting

And tons more…

 

Scripting languages in brief -

  1. Uses interpreter: Scripting languages use an interpreter instead of the compiler (No need to convert code to assembly/machine language)
  2. Easy learning: Easy to learn and can be edited on the go, unlike compiler-based languages no need to compile once edited.
  3. Highly Interactive: It helps in adding visualization interfaces and combinations in web pages. Modern web pages demand the use of scripting languages. To create enhanced web pages, fascinated visual description which includes background and foreground colors, and so on.

 

PowerShell - Important to know

A little theory about PowerShell, I promise not to be boring here.

PowerShell is a cross-platform task automation and configuration management framework, consisting of a command-line shell and scripting language. Unlike most shells, which accept and return text, PowerShell is built on top of the .NET Common Language Runtime (CLR) and accepts and returns .NET objects. This fundamental change brings entirely new tools and methods for automation.

  • PowerShell produces the object-based output:  What is the object-based output? Let’s understand -
  • If I run a command on BASH or SH, it returns a collection of string (a lot of text on screen). On other hand in PowerShell, we get objects (having properties to play with).
  • We can play with the object properties, can use the output object as input on other commands. This property makes it very flexible and powerful.
    • Pipelines: Pipelines help us to take input from the output of another command.
    • Get-Member: To check the object type
  • Support for legacy CMD commands and configurable Aliases: PowerShell supports variety of legacy commands used by legacy Command Prompt. We can manually set Aliases for your favorite cmdlets (PowerShell commands called cmdlets).

 

Starting with PowerShell

PowerShell V/S PowerShell ISE -

  1. PowerShell: It’s a command-line utility where you run commands one at a time.
  2. PowerShell ISE: PowerShell Integrated Scripting Environment is a Graphical UI where you can create scripts.    

ISE has many great features -

  • Syntax highlighting
  • Recover unsaved files (Only if ISE closed abnormally)
  • Code suggestions tray
  • Error highlighting
  • Integrated PowerShell inside to run scripts on the go.
  • Available on all Current Windows Platforms
  • Many more great features…

 

Launching PowerShell and run basic commands -

Search for PowerShell on your Windows Programs menu (Windows + S to search)

Let's try our first command - Get-Process

This command returns all running processes on your Windows System as follows (Number or processes could be different in your case) -

Handles  NPM(K)    PM(K)      WS(K)     CPU(s)     Id  SI ProcessName
-------  ------    -----      -----     ------     --  -- -----------
   1914      33    10564      14196               996   0 lsass
    907      75    42576      28084              1656   0 SearchIndexer
    549      38     6588       5836      49.13   2380   5 AuthManSvr
    503      31     8452      11016     102.22   2384   5 AdobeCollabSync
    193      19     3092       7168      40.61   3272   5 SecurityHealthSystray
    192      10     2592       3496              3572   0 wlanext
     64       6     1044       1780              3628   0 ELANFPService
    430      31     9304      24532       0.39   3688   5 smartscreen
    121       8     1552       1472              4032   0 armsvc
    290      22     7344       4088              4084   0 UpdaterService
    388      31    18584       6408              4116   0 IntelAudioService
    307      12     2452       2652              4344   0 RtkAudUService64

 

On GUI applications like File Explorer, you generally use and   like buttons to navigate through directories. But here in PowerShell or in BASH, we use commands as bellow - 

  • Set-Location Change Directory
  • Set-Location .. Go to one directory back (Parent Directory/Folder)
  • Set-Location / Go to root directory/Folder.
  • Set-Location 'c:\path\to\folder' Go to specific folder path.
  • Set-Location 'NameOfFolder' Go to a folder inside current folder

You can also use Alias cd instead of Set-Location, works same.

Checking/listing all available Folders/Files inside.current directory -

  • Get-ChildItem Listing all available folders and Files
  • ls and dir are alias for Get-ChildItem
  • Get-ChildItem -Force (Use -Force parameter to display hidden Files/Folders as well)

 

Building blocks of PowerShell

Verb and Nouns are two building blocks of PowerShell. Let's understand this using some examples -

  • Verbs:   Get , Set , New , Import , Install , Export , etc.. are  starting block of a cmdlet in PowerShell.
  • Nouns:   Process , Event , ChildItem , Location , Item , LocalUser etc.. are ending block of cmdlet. 

 

Note:   PowerShell is not Case-sensitive. Although it's a good practice to use CamelCasing if we have more then one nouns to use. e.g. ChildItem ,  LocalUser in this scenario.

Combination of Verb-Nouns make a cmdlet. e.g. Get-Process, Get-EventLog, Get-ChileItem, Set-Location, New-item, etc.. 

Use command Get-Command * to get list of all available cmdlets on your System.

 

Parameters -

Parameters are used when we want to manipulate the default values provided in a cmdlet while running it. Let's learn it using an example -

 By default Get-Process gives you all running processes on your Local Machine. If you want to Get processes on remote machine, you need to use  Get-Process -ComputerName “ComputerName” where -ComputerName is Parameter and “ComputerName” is value of parameter.

 

PS C:\Users\kamal >  Get-Process -ComputerName "VM-TechAware-1"

Handles  NPM(K)    PM(K)      WS(K)     CPU(s)     Id  SI ProcessName
-------  ------    -----      -----     ------     --  -- -----------
    373      21     7668       1552       0.36   6228   2 AcrobatNotificationClient
    514      32     9008      11240      72.50   8392   2 AdobeCollabSync
    307      24     4984       6636      32.39  10312   2 AdobeCollabSync
    493      36    20684      14376      33.70   3592   2 ApplicationFrameHost
    121       8     1524       1416              4088   0 armsvc
    272      13     3008       2060              4060   0 AsusLinkNear
    188      10     5368       1312              4072   0 AsusLinkRemote
    142       8     1540        564              3512   0 AsusOptimization
    149      18     2572       2368      28.66   7984   2 AsusOptimizationStartupTask

 

Notes:

1.  You can use multiple parameters if applicable on that cmdlet.

2.  Hyphen ( - ) used before name of Parameter, so that PowerShell can understand difference between Parameters and it's values.

3.  Get-Help cmdlet-name can be used to know more about commands and it's parameters. You can Check my article PowerShell ~ How to use Get-Help cmdlet to know about Get-Help more.

4.  Few parameters can be without values, e.g. -Force  used for forcefully run cmdlets (Not available for all cmdlets)

 

Basic commands - 

 

Let's see few daily use commands which you can start practicing with…

  • Restart-Computer Restarts your computer instantly.
  • Restart-Computer -ComputerName “RemoteComputerName” Restarts remote computer instantly. Use -Force parameter if user is logged-in on remote computer, and you still want to get it restarted.
  • Get-Process gets list of all available processes.
  • Stop-Process -Name 'Notepad' this command will stop Notepad process.
  • Clear-Host clears the current PowerShell Screen (Shortcut - Ctrl + L)
  • Get-Date gives you current date
  • Get-ComputerInfo gives you detailed information about your computer.

You can play with these commands to start with PowerShell

Tip: 

Search for cmdlets using Get-Command -Name “Get-Computer* using * you can search on basis of Wildcards.

Use multiple * Get-Command -Name “*Computer* if you don't know starting, ending or middle of a command. 

 

Our first PowerShell Script 

 

Let's open PowerShell ISE and write down a script to Add 2 numbers.

# Asking user for input
[int]$num1 = Read-Host "Enter 1st number"
[int]$num2 = Read-Host "Enter 2nd number"

# Doing math
$result = $num1 + $num2

# Displaying result
Write-Host "The Sum of $num1 and $num2 is $result"

I know above 7 lines script is much difficult to understand if you're not from development background. Let's understand each line one by one.

  1. # Asking user for input Any line starting with pound (#) is a comment. This will be ignored by PowerShell while running script. Comments make our scripts easier to understand.
  2. [int]$num1 = Read-Host "Enter 1st number"
    1. [int] stands for integer. It is optional in many cases. We have many more variable types like [string] etc.
    2. $num1 It's a variable. We can store any kind of value into variables and use them within script.[int] defined type of variable, so that PowerShell knows what type of value we want users to insert. It is optional.
    3. Read-Host is a cmdlet which takes any string "Enter 1st number" as argument. Read-Host reads the input from user.
  3. # Doing math It's a comment
  4. $result = $num1 + $num2 Here we're defining $result variable which is containing value of SUM of $num1 and $num2 where + is operator used to for addition ( + concatenation in case of adding 2 strings ). There are more operators like -, *, /, % etc.. % is modules operator returns remainder after dividing 2 numbers.
  5. # Displaying result it's a comment
  6. Write-Host "The Sum of $num1 and $num2 is $result" write-host used to display something on screen. Using "" you can enter the information you want to display. variables defined with $ will automatically substituted with it's values. Use '' if you want only text to be displayed

 

Result of above script -

Save the script as AnyFileName.ps1 run the script on PowerShell ISE, User green color PLAY button. 

The result would be similar to this -

PS C:\Users\kamal> C:\Users\kamal\Downloads\add-numbers.ps1
Enter 1st number: 650
Enter 2nd number: 750
The Sum of 650 and 750 is 1400

PS C:\Users\kamal> 

 

PowerShell on Linux

 

Installation on Ubuntu -

# Download the Microsoft repository GPG keys
wget -q https://packages.microsoft.com/config/ubuntu/16.04/packages-microsoft-prod.deb

# Register the Microsoft repository GPG keys
sudo dpkg -i packages-microsoft-prod.deb

# Update the list of products
sudo apt-get update

# Install PowerShell
sudo apt-get install -y powershell

# Start PowerShell
pwsh

Installation on Fedora - 

# Register the Microsoft signature key
sudo rpm --import https://packages.microsoft.com/keys/microsoft.asc

# Register the Microsoft RedHat repository
curl https://packages.microsoft.com/config/rhel/7/prod.repo | sudo tee /etc/yum.repos.d/microsoft.repo

# Update the list of products
sudo dnf check-update

# Install a system component
sudo dnf install compat-openssl10

# Install PowerShell
sudo dnf install -y powershell

# Start PowerShell
pwsh

 

For other versions of Linux, you can visit Microsoft Docs - Installing PowerShell on Linux

 

Later on this PowerShell series of lectures, we'll start exploring Microsoft Azure's cmdlets, deploying cloud resources, managing network, etc.