Arrays in PowerShell - Mini Project: Build & Apply

Working with Arrays in PowerShell

📖 Scenario: You are organizing a small event and need to manage a list of guest names using PowerShell arrays.

🎯 Goal: Build a PowerShell script that creates an array of guest names, adds a new guest, filters guests whose names start with a specific letter, and then displays the filtered list.

📋 What You'll Learn

Create an array with exact guest names

Add a new guest name to the array

Filter the array for names starting with a specific letter

Print the filtered list of guest names

💡 Why This Matters

🌍 Real World

Managing lists of items like guest names, file names, or tasks is common in automation scripts.

💼 Career

Knowing how to work with arrays and filter data is essential for system administrators and automation engineers.

1

Create the initial array of guest names

Create an array called guests with these exact names: "Alice", "Bob", "Charlie", "Diana", and "Ethan".

PowerShell

# Create the array called guests with the exact names
# Your code here

Hint

Use @() to create an array and separate names with commas.

2

Add a new guest name to the array

Add the guest name "Fiona" to the existing guests array using the += operator.

PowerShell

$guests = @("Alice", "Bob", "Charlie", "Diana", "Ethan")
# Add "Fiona" to the guests array
# Your code here

Hint

Use $guests += "Fiona" to add a new item to the array.

3

Filter guests whose names start with the letter 'C'

Create a new array called filteredGuests that contains only the names from guests starting with the letter 'C'. Use the Where-Object cmdlet with a script block checking if the name starts with 'C'.

PowerShell

$guests = @("Alice", "Bob", "Charlie", "Diana", "Ethan")
$guests += "Fiona"
# Filter guests starting with 'C' into filteredGuests
# Your code here

Hint

Use Where-Object { $_.StartsWith('C') } to filter names starting with 'C'.

4

Display the filtered guest names

Print the contents of the filteredGuests array using Write-Output.

PowerShell

$guests = @("Alice", "Bob", "Charlie", "Diana", "Ethan")
$guests += "Fiona"
$filteredGuests = $guests | Where-Object { $_.StartsWith('C') }
# Print the filteredGuests array
# Your code here

Hint

Use Write-Output $filteredGuests to display the filtered names.

Practice

1. What does an array in PowerShell do?

easy

A. Stores only one item at a time

B. Stores multiple items in one variable

C. Runs commands sequentially

D. Creates a new script file

Solution

1. Step 1: Understand the purpose of arrays

   Arrays hold multiple values together in one variable, unlike single variables that hold one value.

2. Step 2: Compare options with array definition

   Only Stores multiple items in one variable correctly describes storing multiple items in one variable, which matches the array concept.

3. Final Answer:

   Stores multiple items in one variable -> Option B

4. Quick Check:

   Arrays = store multiple items [OK]

Hint: Arrays hold many items together in one variable [OK]

Common Mistakes:

• Thinking arrays hold only one item
• Confusing arrays with scripts or commands
• Believing arrays create files

2. Which of the following is the correct way to create an empty array in PowerShell?

easy

A. $arr = []

B. $arr = array()

C. $arr = {}

D. $arr = @()

Solution

1. Step 1: Recall PowerShell array syntax

   PowerShell uses @() to create arrays, including empty ones.

2. Step 2: Check each option

   $arr = @() uses @() which is correct. Options A, B, and C use invalid or different syntax for arrays.

3. Final Answer:

   $arr = @() -> Option D

4. Quick Check:

   Empty array = @() [OK]

Hint: Use @() to create arrays in PowerShell [OK]

Common Mistakes:

• Using [] which is not valid for arrays in PowerShell
• Using {} which is for hashtables or script blocks
• Using array() which is not recognized in PowerShell

3. What is the output of this PowerShell code?

$arr = @('apple', 'banana', 'cherry')
Write-Output $arr[1]

medium

A. banana

B. apple

C. cherry

D. 1

Solution

1. Step 1: Understand array indexing in PowerShell

   Arrays start at index 0, so $arr[0] = 'apple', $arr[1] = 'banana', $arr[2] = 'cherry'.

2. Step 2: Identify the output of $arr[1]

   The code outputs the item at index 1, which is 'banana'.

3. Final Answer:

   banana -> Option A

4. Quick Check:

   Index 1 = banana [OK]

Hint: Arrays start at zero; index 1 is second item [OK]

Common Mistakes:

• Thinking index starts at 1
• Confusing item values with index numbers
• Expecting all items printed instead of one

4. Identify the error in this PowerShell code:

$arr = @()
$arr + 'orange'

medium

A. += operator is missing to add item

B. Array cannot be empty

C. Use [] instead of @() for arrays

D. Variable name must start with capital letter

Solution

1. Step 1: Check how to add items to arrays

   In PowerShell, to add an item to an array, use '+=' operator, not just '+'.

2. Step 2: Analyze the code

   The code uses '$arr + 'orange'' which does not update $arr. It should be '$arr += 'orange'' to add the item.

3. Final Answer:

   += operator is missing to add item -> Option A

4. Quick Check:

   Add item with += [OK]

Hint: Use += to add items to arrays, not just + [OK]

Common Mistakes:

• Using + without = to add items
• Thinking arrays cannot be empty
• Confusing array syntax with other languages

5. You have an array $arr = @('cat', 'dog', 'bird'). How do you add 'fish' to the end and then print all items one per line?

hard

A. $arr = $arr + 'fish'; Write-Host $arr

B. $arr + 'fish'; Write-Output $arr

C. $arr += 'fish'; $arr | ForEach-Object { Write-Output $_ }

D. $arr += 'fish'; Write-Host $arr[0], $arr[1], $arr[2], $arr[3]

Solution

1. Step 1: Add 'fish' to the array correctly

   Use '+=' operator to add 'fish' to $arr: $arr += 'fish'.

2. Step 2: Print each item on its own line

   Use pipeline with ForEach-Object and Write-Output to print each item separately.

3. Step 3: Check each option

   $arr += 'fish'; $arr | ForEach-Object { Write-Output $_ } correctly adds and prints items line by line. $arr + 'fish'; Write-Output $arr does not update $arr. $arr = $arr + 'fish'; Write-Host $arr uses Write-Host which prints all items on one line. $arr += 'fish'; Write-Host $arr[0], $arr[1], $arr[2], $arr[3] prints items but manually and is less flexible.

4. Final Answer:

   $arr += 'fish'; $arr | ForEach-Object { Write-Output $_ } -> Option C

5. Quick Check:

   Add with += and print with pipeline [OK]

Hint: Add with += and print each item using pipeline [OK]

Common Mistakes:

• Using + without = to add items
• Printing array without pipeline for separate lines
• Using Write-Host which prints all on one line