PowerShell

What's inside

What is PowerShell, and how does it differ from Command Prompt or Bash?

PowerShell is an object-oriented shell and scripting language built on .NET, unlike CMD or Bash which are text-based and string-oriented.

What is a cmdlet in PowerShell?

Cmdlets are built-in PowerShell commands with a Verb-Noun naming convention that return .NET objects.

What is the purpose of the pipeline (`|`) in PowerShell?

It passes objects from one command to another, enabling powerful data manipulation.

What are PowerShell providers?

Providers give access to different data stores like the file system, registry, and certificate store as if they were file systems.

What is `$null` in PowerShell?

`$null` represents an absence of value or object.

How do you check for `$null` safely?

Use `$null -eq $variable` to avoid errors.

What are common data types in PowerShell?

String, Int, Bool, Array, Hashtable, PSCustomObject.

How do you define a variable in PowerShell?

Using the `$` prefix, e.g., `$name = 'Alice'`.

What is variable scope in PowerShell?

Scope defines where a variable is accessible: Global, Script, Local, or Private.

How do you declare an array in PowerShell?

$array = @(1, 2, 3)

What is a hashtable in PowerShell?

A collection of key-value pairs: `$hash = @{ Key = 'Value' }`

What is a PSObject?

A flexible object type for creating structured output.

What does `Get-Member` do?

Displays the properties and methods of an object.

How do you discover available cmdlets?

Use `Get-Command`.

What is `Out-Null` used for?

Suppresses output by sending it to null.

What is the difference between `Write-Output` and `Return`?

`Write-Output` sends data to the pipeline; `Return` exits a function with a value.

What are aliases in PowerShell?

Shortcuts for cmdlets, e.g., `ls` for `Get-ChildItem`.

What does `Select-Object` do?

Selects specified properties of an object.

How do you define a function in PowerShell?

Use `function FunctionName {}` syntax.

What is the purpose of the `param()` block?

Defines parameters that a script or function accepts.

What is a script block and how is it used?

A block of code enclosed in `{}` that can be passed or executed.

What are the differences between `function` and `filter`?

`filter` is optimized for pipeline input and processes one object at a time.

How do you comment code in PowerShell?

Single line comments use #, multi-line comments use <# #>.

What is the difference between `Write-Output`, `Write-Host`, and `Write-Verbose`?

`Write-Output` sends to pipeline, `Write-Host` writes to console, `Write-Verbose` logs when enabled.

What is the purpose of `Get-Help` and how do you use it?

Displays cmdlet documentation, e.g., `Get-Help Get-Service -Full`.

How can you discover available parameters of a cmdlet?

Use `Get-Command <cmdlet> | Select-Object -ExpandProperty Parameters`.

How do you use `if`, `else`, and `elseif` in PowerShell?

Conditional branching using `if (condition) {}` blocks.

What is the syntax for `foreach`, `while`, and `do-while` loops?

`foreach ($i in $array) {}`, `while (condition) {}`.

How do you exit a loop prematurely?

Use the `break` keyword.

How can you handle looping through a list of servers?

Use a `foreach` loop with an array of server names.

How do you set `$ErrorActionPreference`, and why?

To control error behavior: `Stop`, `Continue`, etc.

What does `-ErrorAction` do?

Overrides error action for individual commands.

What is `$?`, `$LASTEXITCODE`, and `$Error` used for?

`$?` is last command status, `$LASTEXITCODE` is exit code, `$Error` is error stack.

How do you securely prompt for user credentials?

Use `Get-Credential`.

How can you store and reuse credentials in PowerShell?

Export-CliXml protects SecureStrings with DPAPI on Windows only; on Linux and macOS they are not encrypted. Prefer the SecretManagement and SecretStore modules.

What are SecureStrings and how are they used?

Encrypted strings used for storing passwords.

How do you run a script as a different user?

Use `Start-Process -Credential`.

How can PowerShell be used to manage Windows permissions?

Use `Get-Acl` and `Set-Acl`.

What is PowerShell Remoting and how does it work?

Enables remote command execution, over WinRM on Windows and over SSH on any platform in PowerShell 7.

How do you use `Invoke-Command` and `Enter-PSSession`?

`Invoke-Command` runs code remotely; `Enter-PSSession` starts an interactive session.

What are background jobs in PowerShell?

Asynchronous tasks started with `Start-Job`.

How do you use `Start-Job` and `Receive-Job`?

To start and retrieve results from background jobs.

How can you automate a PowerShell script to run on a schedule?

Use Task Scheduler or Register-ScheduledTask on Windows, or Azure Automation in the cloud.

What is a PowerShell module and how do you import one?

A collection of cmdlets/functions; use `Import-Module`.

What is a PowerShell profile and what is it used for?

A script that runs on shell startup for environment setup.

How do you create reusable tools or scripts across different sessions?

Save as modules and load via profile or Import-Module.

How can you create custom aliases or functions in your profile?

Edit `$PROFILE` to include `Set-Alias` or functions.

What is the difference between `$PROFILE`, `$MyInvocation`, and `$PSScriptRoot`?

`$PROFILE` is the profile path, `$MyInvocation` provides script context, `$PSScriptRoot` is the script's folder path.

What is the difference between functions and cmdlets?

Cmdlets are compiled commands built in .NET, while functions are scripts written in PowerShell.

How do you handle errors in PowerShell?

Use try/catch/finally blocks and the $Error variable for error handling.

What is the difference between -eq and -like operators?

-eq tests equality, while -like supports wildcard pattern matching.

What is the difference between $null and empty string?

$null means no value, an empty string is a value of zero length.

What is the difference between foreach and ForEach-Object?

'foreach' is a language keyword, ForEach-Object is a cmdlet that processes pipeline input.

How do you read user input?

Use Read-Host cmdlet.

What is the purpose of the 'Get-Process' cmdlet?

Retrieves information about running processes.

How do you filter objects in a pipeline?

Using the Where-Object cmdlet or the ? alias.

How do you sort objects?

Use Sort-Object cmdlet.

How do you convert strings to other data types?

Using type casting or methods like [int]'123'.

How do you handle JSON data in PowerShell?

Use ConvertFrom-Json and ConvertTo-Json cmdlets.

What is the difference between $PSVersionTable and $Host?

$PSVersionTable shows PowerShell version info, $Host gives host environment info.

How do you execute external programs from PowerShell?

By calling the executable directly, e.g., notepad.exe.

How do you check if a file exists?

Use Test-Path cmdlet.

How do you stop a running script?

Use Ctrl+C or throw a terminating error.

How do you export data to CSV?

Using Export-Csv cmdlet.

How do you import data from CSV?

Using Import-Csv cmdlet.

How do you define default values for parameters?

Within the param block, e.g. [string]$name = 'default'.

How do you check the PowerShell execution policy?

Use Get-ExecutionPolicy cmdlet.

How do you change the execution policy?

Using Set-ExecutionPolicy cmdlet with appropriate permissions.

How do you iterate through a hashtable?

Using foreach with $hashtable.GetEnumerator().

How do you handle modules in PowerShell?

Install via Install-Module and import using Import-Module.

What is 'Pipeline Variable'?

A variable that holds the current object in the pipeline, accessed via ForEach-Object -PipelineVariable.

How do you run a script asynchronously?

Use Start-Job or run scripts in a separate PowerShell session.

How do you handle output redirection?

Use > for stdout, 2> for stderr.

What is the difference between functions and scripts?

Functions are reusable blocks inside scripts or sessions; scripts are standalone files.

How do you use parameter validation?

Use attributes like [ValidateSet()], [ValidateRange()] in param blocks.

What is the difference between -and and &&?

-and is a logical operator on boolean expressions. In PowerShell 7 and later, && and || are pipeline chain operators that run the next command based on the previous command's success; Windows PowerShell 5.1 does not have them.

What is the 'Begin', 'Process', and 'End' blocks in advanced functions?

Special blocks for pipeline processing stages.

How do you handle errors non-terminating vs terminating?

Terminating errors can be caught by try/catch; non-terminating need ErrorAction parameter.

What is the 'dynamic parameters' feature?

Parameters that are added dynamically during runtime.

How do you format output?

Using Format-Table, Format-List, or Format-Custom cmdlets.

How do you debug scripts?

Using Set-PSBreakpoint, Write-Debug, and the VS Code PowerShell debugger (the Windows-only ISE is deprecated).

What is the purpose of 'Get-Content'?

Reads contents of a file.

How do you write to a file?

Using Out-File, Set-Content, or Add-Content cmdlets.

How do you manipulate XML in PowerShell?

Load XML into [xml] typed variable and use XPath.

How do you manage credentials securely?

Use Get-Credential to prompt, and store secrets with the SecretManagement module backed by a vault such as SecretStore or an external secret manager.

How do you pass arguments to a script?

By position or named parameters when invoking the script.

What is the difference between $args and param()?

$args is an automatic array for unnamed arguments; param() defines named parameters.

How do you check for running jobs?

Use Get-Job cmdlet.

How do you stop a job?

Use Stop-Job cmdlet.

What is a PowerShell session?

A persistent connection to a remote or local instance.

How do you create a remote session?

Using New-PSSession cmdlet.

How do you import commands from a remote session?

Use Import-PSSession cmdlet.

What is Desired State Configuration (DSC)?

A management platform for configuration as code using PowerShell.

What is the difference between Write-Verbose and Write-Debug?

Write-Verbose is for general info, Write-Debug is for debugging output.

What are common parameter attributes?

Mandatory, Position, HelpMessage, ValidateSet.

How do you sign PowerShell scripts?

Use Set-AuthenticodeSignature with a code signing certificate.

How do you work with environment variables?

Access via $env:VariableName.

What is the difference between splatting and normal parameter passing?

Splatting passes parameters as a hashtable or array, improving readability.

What is the PowerShell pipeline, and how does it work internally?

The pipeline passes objects, not text, between cmdlets enabling rich object manipulation.

Explain how PowerShell uses the .NET framework.

PowerShell is built on .NET, allowing direct access to .NET classes and libraries.

How do you create and use modules?

Modules are reusable packages of functions, cmdlets, and variables, imported via Import-Module.

What is the difference between script scope and global scope?

Global scope variables are accessible everywhere; script scope is limited to the script.

What is the difference between value types and reference types in PowerShell?

Value types store data directly, reference types store pointers to data.

How does PowerShell handle type conversion?

PowerShell performs implicit and explicit type conversion, using casting and .NET methods.

What is an advanced function?

Functions that behave like cmdlets with support for parameters, pipeline input, and more.

How do you write a PowerShell function that accepts pipeline input?

Define parameters with ValueFromPipeline or ValueFromPipelineByPropertyName.

What is the difference between a parameter and an argument?

Parameter is defined in the function signature, argument is the value passed.

Explain how PowerShell handles memory management.

Relies on .NET garbage collection for managing memory.

What are attributes in PowerShell?

Metadata added to parameters or functions to modify behavior.

What is reflection in PowerShell?

Accessing metadata about objects, types, and assemblies at runtime.

How do you create custom objects in PowerShell?

Use New-Object, PSCustomObject, or .NET classes.

What is the difference between synchronous and asynchronous commands?

Synchronous commands block until complete; asynchronous run concurrently.

Explain the concept of cmdlet binding.

Enables advanced features like parameter validation and pipeline support in functions.

How do you trap errors globally in a script?

Use the trap statement or set $ErrorActionPreference.

How do you manage multithreading in PowerShell?

Use ForEach-Object -Parallel (PowerShell 7), thread jobs via Start-ThreadJob, background jobs, or runspaces. Workflow parallelism existed only in Windows PowerShell 5.1.

What are runspaces?

Lightweight PowerShell execution environments allowing parallel execution.

How do you serialize and deserialize objects in PowerShell?

Using Export-CliXml and Import-CliXml.

Explain the difference between Add-Type and using assemblies.

Add-Type compiles code on the fly; loading assemblies imports precompiled libraries.

How can you improve script performance?

Minimize pipeline usage, avoid unnecessary loops, use native cmdlets.

What is dot-sourcing?

Running a script in the current scope to import functions and variables.

How do you implement logging in PowerShell scripts?

Use transcript, Write-Verbose, Write-Information, or custom log files.

How do you manage dependencies between scripts?

Using modules and Import-Module or dot-sourcing.

How do you secure PowerShell scripts?

Use execution policies, code signing, credential management, and constrained endpoints.

How do you create GUI applications with PowerShell?

Using Windows Presentation Foundation (WPF) or Windows Forms.

What is the role of the PowerShell console host?

It hosts the PowerShell engine and provides the user interface.

What is the 'using' statement in PowerShell 5.0+?

Allows importing namespaces or modules at the top of scripts.

How do you debug remote PowerShell sessions?

Using Enter-PSSession with debugging enabled and VSCode integration.

What is a PowerShell workflow?

A Windows PowerShell 5.1 feature for long-running, restartable, parallelizable scripts. Removed in PowerShell 7; use jobs, ForEach-Object -Parallel, or an external orchestrator instead.

Explain how PowerShell supports REST APIs.

Using Invoke-RestMethod and Invoke-WebRequest cmdlets.

How do you use regular expressions in PowerShell?

With -match, -replace operators and .NET regex classes.

How do you ensure idempotency in PowerShell scripts?

Check current state before making changes; avoid side effects.

Explain how PowerShell supports cross-platform scripting.

PowerShell 7 (formerly called PowerShell Core) runs on Windows, Linux, and macOS with consistent commands.

How do you use DSC to enforce configuration state?

Define configurations in scripts and apply them using Start-DscConfiguration.