PowerShell Interview Questions and Answers

This section covers a broad range of PowerShell interview questions, from fundamental concepts to more advanced scripting techniques and error handling.

What is PowerShell?

PowerShell is a task-based command-line shell and scripting language built on the .NET framework. It's designed for system administrators and power users to manage Windows systems and automate tasks. It's now open source and available on multiple platforms.

Key Features of PowerShell

• Object-based: Commands return objects, not just text, allowing for more powerful manipulation.
• Customizable commands (cmdlets): You can create your own cmdlets.
• PowerShell Remoting: Run commands remotely on other systems.
• Robust scripting and debugging capabilities: Facilitates creating and debugging scripts.

Launching PowerShell in Windows

1. Search for "PowerShell" in the Windows search bar.
2. Select "Windows PowerShell" to launch it.

PowerShell Pipelines

A pipeline in PowerShell chains commands together using the pipe symbol (|). The output of one command becomes the input for the next.

Get-Process | Where-Object {$_.CPU -gt 50} | Select-Object Name, CPU

PowerShell Execution Policies

Execution policies control which scripts PowerShell can run. This is a security feature.

Types of Execution Policies

• AllSigned: Only signed scripts.
• RemoteSigned: Local scripts; downloaded scripts must be signed.
• Restricted: No scripts (default for many Windows client installations).
• Undefined: No policy set.
• Bypass: No restrictions (use with caution).
• Unrestricted: Runs any script without warnings (default for many non-Windows systems).

try...catch...finally in PowerShell

Error handling in PowerShell:

• try: Block of code to be monitored for errors.
• catch: Handles errors that occur in the try block.
• finally: Code executed regardless of whether an error occurred. (Often used for cleanup.)

CIM (Common Information Model) vs. WMI (Windows Management Instrumentation)

The $input Variable

The $input automatic variable provides access to data passed through a pipeline in PowerShell. It represents the input stream for a function or script.

PowerShell vs. CMD (Command Prompt)

Comments in PowerShell

• Single-line comments: # ...comment...
• Multi-line comments: <# ...comment... #>

PowerShell Brackets

• {}: Code blocks.
• (): Function arguments.
• []: Array indexing, optional parameters.

PowerShell Variables

PowerShell variables start with a dollar sign ($). They can hold various data types (numbers, strings, objects).

Declaring and Creating Variables

$myVariable

$myVariable = "Hello"

Extending PowerShell

• PSSnapins (older method)
• Modules (recommended approach)

Pipeline Input Methods

• ByValue
• ByPropertyName

Types of PowerShell Variables

• User-defined variables
• Automatic variables
• Preference variables

Automatic Variables

Automatic variables are predefined variables containing information about the PowerShell environment and the current execution context.

• $PSVersionTable: PowerShell version information.
• $?: Success/failure status of the last command.
• $_: The current object in a pipeline.
• $args: Arguments passed to a function.
• $Error: Contains error information.

Arrays in PowerShell

Arrays store ordered collections of items.

Hash Tables

Hash tables (associative arrays) store key-value pairs. Keys must be unique.

$hash = @{key1 = 'value1'; key2 = 'value2'}

PowerShell Operators

[List different types of PowerShell operators (arithmetic, assignment, comparison, logical, etc.).]

Comparison Operators

[Describe PowerShell's comparison operators (equality, match, containment, replacement).]

Cmdlets

Cmdlets are commands in PowerShell that follow a verb-noun naming convention (e.g., Get-Process, Set-Location). They return .NET objects.

Loops in PowerShell

PowerShell provides various loop structures:

• while
• do...while
• for
• foreach

Types of Loops in PowerShell

In PowerShell, there are several types of loops that allow you to execute a block of code multiple times. Here's a description of each type of loop:

1. while Loop

The while loop executes the block of code as long as the specified condition evaluates to true.

while () {
    # Code to execute
}

# The loop will continue running until the condition is false.

2. do...while Loop

The do...while loop is similar to the while loop, but it always executes the code block at least once before checking the condition.

do {
    # Code to execute
} while ()

# The loop will always execute at least once before checking the condition.

3. for Loop

The for loop is ideal when the number of iterations is known beforehand. It includes initialization, condition checking, and iteration.

for (; ; ) {
    # Code to execute
}

# The loop will run a specific number of times based on the given condition.

4. foreach Loop

The foreach loop is used to iterate over a collection, such as an array or a list. It executes the code block for each item in the collection.

foreach ($item in ) {
    # Code to execute
}

# The loop will execute the block of code for each item in the collection.

Copying Files, Registry Keys, and Folders

The Copy-Item cmdlet copies items in the file system and registry.

Data Formatting Cmdlets

PowerShell cmdlets for formatting data:

• Format-List
• Format-Table
• Format-Wide
• Format-Custom

Renaming Variables in PowerShell

Use the Rename-Item cmdlet to rename variables (treating them as items in the variable drive):

Rename-Item -Path variable:\oldName -NewName newName

Get-Command Cmdlet

The Get-Command cmdlet retrieves information about available commands (cmdlets, functions, aliases, scripts).

Executing PowerShell Scripts

1. Write the script in a text editor.
2. Save it with a .ps1 extension.
3. Run the script from the PowerShell console by typing its name.