N.R.DAS: 50 PowerShell Interview Questions and Answers

This post provides a comprehensive list of 50 Common PowerShell interview questions along with their detailed answers. This guide covers a wide range of topics, from fundamental concepts to advanced scripting and administration, designed to help you prepare for your next interview.

Basic Concepts

Q: What is PowerShell and what is its primary purpose?
- A: PowerShell is a cross-platform task automation and configuration management framework from Microsoft, consisting of a command-line shell and a scripting language. Its primary purpose is to automate administrative tasks, manage systems, and interact with various services and applications.
Q: What is a Cmdlet? How do you identify a Cmdlet?
- A: A Cmdlet (pronounced "command-let") is a lightweight command used in the PowerShell environment. Cmdlets are identified by their Verb-Noun naming convention (e.g., Get-Service, Set-Item, New-Module).
Q: What is the difference between a function and a Cmdlet?
- A: Cmdlets are compiled .NET classes written in languages like C# and are designed for specific, atomic tasks. Functions are written in PowerShell scripting language and can combine multiple Cmdlets or other functions to perform more complex operations. Functions are generally more flexible for scripting, while Cmdlets offer better performance and integration with the underlying .NET framework.
Q: How do you get help for a Cmdlet in PowerShell?
- A: You can use the Get-Help Cmdlet. For example, Get-Help Get-Process provides basic help. To get more detailed information, use Get-Help Get-Process -Detailed, Get-Help Get-Process -Examples, or Get-Help Get-Process -Full. To update help files, use Update-Help.
Q: What is the PowerShell pipeline? How does it work?
- A: The PowerShell pipeline is a core feature that allows you to chain commands together, passing the output of one command as the input to another. It works by passing objects (not just text) from left to right. For example, Get-Service | Where-Object {$_.Status -eq 'Running'} | Select-Object Name, Status.
Q: What is the purpose of Get-Member?
- A: Get-Member (alias gm) is used to discover the properties and methods of an object. When you pipe an object to Get-Member, it displays all the available members that can be accessed or manipulated for that object type. This is crucial for understanding what data you can extract or what actions you can perform on an object.
Q: Explain the concept of "Objects" in PowerShell.
- A: Unlike traditional command-line interfaces that often deal with text streams, PowerShell works with objects. When a Cmdlet produces output, it's not just text; it's a structured object with properties (data) and methods (actions). This object-oriented approach allows for powerful filtering, sorting, and manipulation of data in the pipeline.
Q: What are PowerShell providers? Give an example.
- A: PowerShell providers expose data stores (like the file system, registry, or certificate store) as if they were file system drives. This allows you to navigate and manage different data sources using familiar Cmdlets like Get-ChildItem, Set-Item, Remove-Item, etc. Examples include FileSystem, Registry, Certificate, Variable, and Function.
Q: How do you run an external executable (e.g., ipconfig.exe) from PowerShell?
- A: You can simply type the executable name and its arguments, just like in a command prompt. For example, ipconfig /all. PowerShell will execute the external program and display its standard output.
Q: What is the purpose of the $_ variable?
- A: The $_ (or $PSItem) automatic variable represents the current object in the pipeline. It is commonly used within script blocks (e.g., Where-Object, ForEach-Object) to refer to the object being processed at that moment.

Scripting and Advanced Concepts

Q: How do you define a variable in PowerShell?
- A: Variables are defined using a dollar sign ($) followed by the variable name. For example, $myVariable = "Hello World".
Q: What is a PowerShell profile? Why is it useful?
- A: A PowerShell profile is a script that runs automatically when PowerShell starts. It's useful for customizing your environment, defining functions, setting aliases, loading modules, and generally preparing your session for your common tasks. You can find the path to your current user profile using $PROFILE.
Q: How do you create a function in PowerShell?
- A: Functions are created using the function keyword, followed by the function name and a script block.
```
function Get-MyProcess {
    Param (
        [string]$Name
    )
    Get-Process -Name $Name
}
```
Q: Explain the Param block in a PowerShell function.
- A: The Param block defines the parameters that a function accepts. It allows you to specify parameter names, data types, default values, and attributes like [Parameter(Mandatory=$true)] or [Parameter(Position=0)] to control how parameters are used.
Q: What are common parameters in PowerShell? Give examples.
- A: Common parameters are a set of parameters that can be used with almost any Cmdlet. They provide consistent functionality across commands. Examples include:
  - -Verbose: Displays detailed information about the operation.
  - -Debug: Displays programmer-level messages.
  - -WhatIf: Shows what would happen if the command were run, without actually executing it.
  - -Confirm: Prompts for confirmation before executing the command.
  - -ErrorAction: Specifies how the Cmdlet responds to a non-terminating error (e.g., Continue, SilentlyContinue, Stop).
  - -ErrorVariable: Appends error messages to a specified variable.
  - -OutVariable: Saves the output of the command to a specified variable.
  - -OutBuffer: Collects all output before sending it through the pipeline.
Q: How do you handle errors in PowerShell scripts?
- A: PowerShell provides several mechanisms for error handling:
  - Try-Catch-Finally: For terminating errors. Try block contains code that might throw an error, Catch handles the error, and Finally executes regardless of whether an error occurred.
  - Trap: A simpler error handler for a specific scope.
  - -ErrorAction parameter: For non-terminating errors (e.g., Stop, Continue, SilentlyContinue).
  - $Error automatic variable: Contains an array of recent errors.
  - $LASTEXITCODE: For external executables.
Q: What is the difference between $ErrorActionPreference = 'Stop' and using Try-Catch?
- A: $ErrorActionPreference = 'Stop' changes the default behavior for all non-terminating errors in the current scope to become terminating errors. This means they will halt script execution. Try-Catch, on the other hand, is a specific block of code designed to gracefully handle terminating errors within that block, allowing you to define custom logic for recovery or logging without necessarily stopping the entire script.
Q: How do you run a PowerShell script?
- A: You can run a PowerShell script by navigating to its directory and typing its full path and name (e.g., .\MyScript.ps1) or by providing the full path from any location (e.g., C:\Scripts\MyScript.ps1). You might need to adjust the execution policy first.
Q: What is the PowerShell execution policy? How do you change it?
- A: The execution policy is a security feature that controls how PowerShell loads configuration files and runs scripts.
  - Restricted: No scripts can run.
  - AllSigned: Only scripts signed by a trusted publisher can run.
  - RemoteSigned: Downloaded scripts must be signed by a trusted publisher; local scripts don't need to be.
  - Unrestricted: All scripts can run (least secure).
  - Bypass: Nothing is blocked and no warnings are given.
  - Undefined: No execution policy is set for the current scope. You can check the current policy with Get-ExecutionPolicy and change it with Set-ExecutionPolicy <PolicyName>.
Q: How do you pass arguments to a PowerShell script?
- A: Arguments can be passed directly after the script name, similar to Cmdlet parameters. Inside the script, you can define a Param block to receive these arguments.
```
# MyScript.ps1
Param (
    [string]$Message
)
Write-Host "Received message: $Message"
```
  Run: .\MyScript.ps1 -Message "Hello from argument"
Q: What is a hash table in PowerShell? When would you use one?
- A: A hash table (also known as an associative array or dictionary) is a collection of key-value pairs. Keys must be unique. You define them using @{}, e.g., $myHash = @{ Name = "Alice"; Age = 30 }. They are useful for storing structured data, passing multiple named parameters to a function, or creating custom objects.
Q: How do you loop through a collection of items in PowerShell?
- A: You can use ForEach-Object (often aliased as %) or the foreach statement.
  - ForEach-Object (pipeline-oriented): Get-Service | ForEach-Object { Write-Host $_.Name }
  - foreach statement (script-oriented):
```
$services = Get-Service
foreach ($service in $services) {
    Write-Host $service.Name
}
```
Q: What is the difference between Where-Object and Select-Object?
- A:
  - Where-Object (alias where or ?) is used for filtering objects based on specified criteria. It selects which objects to pass down the pipeline. Example: Get-Process | Where-Object {$_.CPU -gt 100}.
  - Select-Object (alias select) is used for selecting which properties of an object to display or pass down the pipeline. It shapes the objects. Example: Get-Process | Select-Object Name, Id, CPU.

Q: How do you convert an object to JSON in PowerShell?

A: Use the ConvertTo-Json Cmdlet.

$data = @{ Name = "Bob"; City = "New York" }
$json = $data | ConvertTo-Json
Write-Host $json

Q: How do you parse JSON from a string in PowerShell?

A: Use the ConvertFrom-Json Cmdlet.

$jsonString = '{"Name":"Bob","City":"New York"}'
$object = $jsonString | ConvertFrom-Json
Write-Host $object.Name

Q: What are PowerShell modules? Why are they important?
- A: PowerShell modules are self-contained units of reusable PowerShell code (Cmdlets, functions, variables, workflows, etc.). They are important because they allow for organization, distribution, and versioning of code, making it easier to share and manage functionality across different scripts and environments.
Q: How do you import and export modules?
- A:
  - Import: Import-Module <ModuleName> (often modules auto-load when a Cmdlet from them is called).
  - Export: You don't explicitly "export" a module in the same way you import it. Instead, you create a module manifest (.psd1 file) or a script module (.psm1 file) that defines what functions/Cmdlets are exposed when the module is imported.
Q: What is the difference between Write-Host, Write-Output, and Write-Verbose?
- A:
  - Write-Host: Writes directly to the console. It's primarily for displaying messages to the user and does not send objects to the pipeline. Often used for formatting output with colors.
  - Write-Output: Sends objects to the pipeline. This is the default behavior of most Cmdlets. If Write-Output is the last command in a function, its output is returned by the function.
  - Write-Verbose: Writes verbose messages to the console. These messages are only displayed when the -Verbose common parameter is used with the Cmdlet or script, or when $VerbosePreference is set to Continue. It's used for debugging and providing detailed execution information.
Q: How do you schedule a PowerShell script to run automatically?
- A: You can schedule a PowerShell script using the Windows Task Scheduler. You would set the action to "Start a program" and specify powershell.exe as the program, with arguments like -File "C:\Path\To\Your\Script.ps1".
Q: What is Desired State Configuration (DSC)?
- A: DSC is a management platform in PowerShell that enables you to deploy and manage configuration data for software services and manage the environment in which these services run. It allows you to define the desired state of your servers and infrastructure using PowerShell scripts, and DSC will ensure that state is maintained.

System Administration and Practical Applications

Q: How do you get a list of all running processes on a system?
- A: Get-Process
Q: How do you stop a specific process by name (e.g., Notepad)?
- A: Stop-Process -Name "notepad" -Force (using -Force to bypass confirmation).
Q: How do you get information about a specific service (e.g., Spooler)?
- A: Get-Service -Name "Spooler"
Q: How do you start a service? How do you stop a service?
- A:
  - Start: Start-Service -Name "ServiceName"
  - Stop: Stop-Service -Name "ServiceName"
Q: How do you list all files and folders in a directory?
- A: Get-ChildItem -Path "C:\MyFolder" or Get-ChildItem -Path "C:\MyFolder" -Recurse for subfolders.
Q: How do you create a new folder?
- A: New-Item -Path "C:\NewFolder" -ItemType Directory
Q: How do you copy a file from one location to another?
- A: Copy-Item -Path "C:\Source\File.txt" -Destination "C:\Destination\"
Q: How do you delete a file? How do you delete a non-empty folder?
- A:
  - Delete file: Remove-Item -Path "C:\File.txt"
  - Delete non-empty folder: Remove-Item -Path "C:\MyFolder" -Recurse -Force

Q: How do you get the IP address of the local machine?

Get-NetIPAddress | Where-Object {$_.AddressFamily -eq 'IPv4' -and $_.InterfaceAlias -like 'Ethernet*'} | Select-Object IPAddress
# Or simpler for common cases:
(Get-NetIPConfiguration).IPv4Address.IPAddress

Q: How do you list all active directory users in a specific Organizational Unit (OU)?
- A: You need the Active Directory module (ActiveDirectory).
```
Import-Module ActiveDirectory
Get-ADUser -Filter * -SearchBase "OU=Users,DC=yourdomain,DC=com"
```

Q: How do you create a new Active Directory user?

A: (Requires Active Directory module)

Import-Module ActiveDirectory
New-ADUser -Name "John Doe" -SamAccountName "jdoe" -UserPrincipalName "jdoe@yourdomain.com" -Path "OU=Users,DC=yourdomain,DC=com" -AccountPassword (ConvertTo-SecureString "Password123!" -AsPlainText -Force) -Enabled $true

Q: How do you restart a remote computer using PowerShell?
- A: Restart-Computer -ComputerName "RemotePC01" (requires appropriate permissions and firewall rules).
Q: How do you get event logs from a specific log name (e.g., System) and filter by event ID?
- A: Get-WinEvent -LogName "System" -FilterXPath "*[System[(EventID=100)]]" or Get-WinEvent -LogName "System" | Where-Object {$_.Id -eq 100}
Q: What is PowerShell Remoting? How do you enable it?
- A: PowerShell Remoting allows you to run PowerShell commands on remote computers. It uses WS-Management (WinRM) protocol. You enable it on the target machine using Enable-PSRemoting.
Q: How do you run a command on a remote computer using PowerShell Remoting?
- A:
  - Invoke-Command: For single commands or script blocks. Invoke-Command -ComputerName "RemotePC01" -ScriptBlock { Get-Service WinRM }
  - Enter-PSSession: To establish an interactive session. Enter-PSSession -ComputerName "RemotePC01" (then you can run commands directly as if you were on the remote machine).

Best Practices and Miscellaneous

Q: What are some best practices for writing PowerShell scripts?
- A:
  - Use Verb-Noun naming for functions and scripts.
  - Add comments to explain complex logic.
  - Use Param blocks for input parameters.
  - Implement robust error handling (Try-Catch).
  - Use Write-Verbose for detailed logging.
  - Use WhatIf and Confirm for destructive operations.
  - Avoid hardcoding paths and credentials.
  - Break down complex scripts into smaller functions.
  - Use Set-StrictMode for better error detection during development.
  - Format your code consistently.
Q: What is Set-StrictMode and why is it useful?
- A: Set-StrictMode enables strict parsing and validation of code. It helps catch common coding errors like using uninitialized variables, referencing non-existent properties, or using functions with incorrect syntax. Setting it to Version 2.0 or Latest is a good practice during script development to ensure code quality.
Q: How do you create a custom object in PowerShell?
- A: You can create custom objects using New-Object PSObject and then adding properties, or more commonly, by casting a hash table to [PSCustomObject]:
```
$myObject = [PSCustomObject]@{
    Name = "Data Point"
    Value = 123
    Timestamp = Get-Date
}
```
Q: What is the purpose of Out-GridView?
- A: Out-GridView sends the output of a command to an interactive, sortable, and filterable graphical window. It's excellent for quickly exploring data, especially when dealing with large datasets, as it provides a user-friendly way to view and manipulate the results without writing complex filtering logic.
Q: How do you convert a CSV file to a PowerShell object and vice-versa?
- A:
  - CSV to Object: Import-Csv -Path "C:\data.csv"
  - Object to CSV: Get-Process | Export-Csv -Path "C:\processes.csv" -NoTypeInformation (-NoTypeInformation prevents adding a #TYPE header row).

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50 PowerShell Interview Questions and Answers

Basic Concepts

Scripting and Advanced Concepts

System Administration and Practical Applications

Best Practices and Miscellaneous

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