Basics of Powershell

Introduction

Windows Powershell is a command line tool from Microsoft to facilitate the system administrators or a developer to interact with the system. When we say it is a command line tool, it means that the user interacts with the system through set of commands.



We simply specify a command through the console window which is as shown above and the Powershell executes the command supplied to it to complete the operation. We can relate the Windows Powershell to the Unix shells such as C-shell or BASH etc.

What is the use of Powershell

Windows Powershell is of great use to the System administrators. The administrators can write scripts using Powershell commands to automate the repetitive administrative tasks, hence reducing the effort of manual work. Also, Powershell provides a rich set of commands which can be used to do not just system administration but a variety of tasks too.

So lets get our hands on Windows Powershell. In your Windows 7/Vista/Windows Server 2008 OS, Go to RUN-> type Powershell and hit enter. You will get a console window.



Here you can see that we have given a Get-Date command and we received the current date-time as the output. So we instructed Powershell with a command and we got a result.

Similarly try and give the command Get-Process which lists all the processes running on your machine. These commands that we write are called "cmdlets". There are huge number of in-built cmdlets. Each command is prefixed with an operation. For example "Get-" in the above two commands that we used: Get-Date and Get-Process. Similarly there is 'Set-', 'Remove-' etc. You can list all the inbuilt Powershell cmdlets by using the command : Get-Command. You can also iterate through the list of Powershell commands one by one. Just type 'Get-' and hit the "TAB" button on your keyboard. For every TAB button hit, Powershell will show you the commands for "Get-" one by one.

So what is the first thing we do when we start learning a new language or a framework? Yes, you guessed it right. The good old "Hello world". So now, we will try writing a simple Hello world to the console window of Powershell. Write the command Write-Host Hello World !!! and hit Enter. The console window will write out the string entered in front of the "Write-Host" command.



Simple enough. Now we will accept some input from the user through the console window and store it in a variable.

Type in the following code

$variable1 = Read-Host

This will take you to the next line where the console is waiting for a user input. I'll enter the string "Hello World !!!". Now we will print this user input to the console using the Write-Host command that we have used above.



Getting help of a CMDLET

You can get the help of a particular CMDLET from the Powershell itself.

For example



Hit Enter



A Tip : If you don't want to write the entire command by yourself and want to enjoy some Intellisense kind of a thing, you can write the command partially and hit the TAB button. The Powershell will complete the command for you.

Eg just type "write-h" and hit TAB. The command Write-Host will appear to the console window.

The commands are not case sensitive. "write-host" is same as "Write-Host"

There is an editor available for writing Powershell scripts- Windows Powershell ISE.



We will write our first script in a simple notepad file.

Open notepad and save the new file as MyFirstPowershellScript.ps1. Enter the following script:

Write-Host `n`n
Write-Host This is a sample Powershell script
Write-Host **********************************
Write-Host `n
Write-Host Enter your first Name :
$firstname = Read-Host
Write-Host Enter your last name :
$lastname = Read-Host
$fullname = $firstname + $lastname
Write-Host Your full name is : $fullname

In the above script

• `n : Denotes a newline on the console window.
• Write-Host : Denotes writing some output to the console window.
• Read-Host : Denotes accepting an input from the user.
• $ : denotes a variable
• + : here denotes that we have concatenated the two strings accepted from the user.

Run a script file

Go To RUN -> Powershell and hit enter. This will open Powershell console window.

We can run the script file as : Complete path of the file\file_name.ps1. If the script resides in the current working directory of the Powershell, we can simply execute it as file_name.ps1

Suppose there is a space in your folder name. For example my script is stored at "D:\scripts\New folder\MyFirstPowershellScript.ps1". If we run the script file just by giving the path, we will get an error.



So in case our path has spaces, we need to run our script as:

&" D:\scripts\New folder\MyFirstPowershellScript.ps1"



In this article we saw how can we create and run a Powershell script. We also saw how we interact with the user through the console window, how can we use variables to store values and retrieve the values from a variable whenever required.