ForEach loop in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of a ForEach loop with array modification

What is the output of this PowerShell script?

PowerShell

$arr = 1,2,3,4
foreach ($i in $arr) {
  $i = $i * 2
  Write-Output $i
}
Write-Output $arr

A

1
2
3
4
1 2 3 4

B

2
4
6
8
2 4 6 8

C

2
4
6
8
1 2 3 4

D

2 4 6 8
2 4 6 8

💡 Hint

Remember that modifying the loop variable inside a ForEach does not change the original array elements.

The loop variable $i is a copy of each element, so changing $i does not affect the original array $arr. The Write-Output inside the loop prints doubled values, but the original array remains unchanged.

📝 Syntax

intermediate

Identify the syntax error in this ForEach loop

Which option contains a syntax error in the ForEach loop?

PowerShell

foreach ($item in $list) {
  Write-Output $item
}

A foreach $item in $list { Write-Output $item }

B foreach ($item in $list) { Write-Output $item }

C } meti$ tuptuO-etirW { )tsil$ ni meti$( hcaerof

D foreach ($item in $list) Write-Output $item

💡 Hint

Check the parentheses around the loop variable.

Option A is missing parentheses around the loop variable and collection, which is required syntax in PowerShell ForEach loops.

🔧 Debug

advanced

Why does this ForEach loop not output anything?

Given this script, why is there no output?

PowerShell

$numbers = 1..5
foreach ($num in $numbers) {
  $num * 2
}

A Because the array $numbers is empty.

B Because the multiplication operator * is invalid in PowerShell.

C Because the foreach loop syntax is incorrect.

D Because the loop variable $num is not being output explicitly.

💡 Hint

In PowerShell, expressions inside loops need to be output explicitly to display.

The expression $num * 2 calculates the value but does not output it. You need to use Write-Output or just place the expression alone to output it.

🚀 Application

advanced

Using ForEach to modify a list of objects

You have a list of objects with a property 'Name'. You want to append '-done' to each Name. Which script correctly updates the objects?

PowerShell

$items = @(
  [PSCustomObject]@{Name='Task1'},
  [PSCustomObject]@{Name='Task2'}
)
foreach ($item in $items) {
  # update Name here
}

A foreach ($item in $items) { $item.Name = $item.Name + '-done' }

B foreach ($item in $items) { $item = $item.Name + '-done' }

C foreach ($item in $items) { $item.Name = $item.Name - '-done' }

D foreach ($item in $items) { $item.Name += '-done' }

💡 Hint

Remember to assign the new string back to the property.

Option A correctly concatenates the string and assigns it back to the Name property. Option A uses += which works but is less clear. Option A replaces the whole object with a string, losing the object structure. Option A uses an invalid operator '-' for strings.

🧠 Conceptual

expert

Understanding pipeline ForEach-Object vs ForEach loop

Which statement about PowerShell's ForEach-Object cmdlet and ForEach loop is TRUE?

A ForEach loop can only process arrays, but ForEach-Object can process any collection.

B ForEach-Object processes items one at a time as they come through the pipeline, while ForEach loop processes all items after the collection is fully available.

C ForEach-Object is faster than ForEach loop because it uses parallel processing by default.

D ForEach loop can be used in pipelines directly, but ForEach-Object cannot.

💡 Hint

Think about how pipeline processing works in PowerShell.

ForEach-Object processes each item as it passes through the pipeline, allowing streaming processing. ForEach loop requires the entire collection before starting the loop.