ForEach-Object for iteration in PowerShell - Step-by-Step Execution

Concept Flow - ForEach-Object for iteration

Input Collection

↓

ForEach-Object Start

↓

Take One Item

↓

Run ScriptBlock on Item

↓

Output Result

↓

More Items?

Yes→Take One Item

No↓

End

ForEach-Object takes each item from a collection, runs a block of code on it, outputs the result, and repeats until all items are processed.

Execution Sample

PowerShell

1..3 | ForEach-Object { $_ * 2 }

This code takes numbers 1 to 3, doubles each, and outputs the results.

Execution Table

Step	Input Item ($_)	Action	Output
1	1	Multiply by 2	2
2	2	Multiply by 2	4
3	3	Multiply by 2	6
4	No more items	Stop iteration	End

💡 All items processed, ForEach-Object ends.

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
$_	null	1	2	3	null

Key Moments - 2 Insights

Why does $_ change each step?

Because $_ represents the current item in the pipeline, it updates to the next item each iteration as shown in execution_table rows 1 to 3.

What happens when there are no more items?

The loop stops as shown in execution_table row 4, because ForEach-Object has processed all input items.

Visual Quiz - 3 Questions

Look at the execution table, what is the output when $_ is 2?

A 4

B 6

C 2

D 8

💡 Hint

Check execution_table row 2 where Input Item is 2 and Output is shown.

At which step does the iteration stop?

A Step 3

B Step 4

C Step 2

D Step 1

💡 Hint

Look at execution_table row 4 where it says 'No more items' and 'Stop iteration'.

If the input was 1..4 instead of 1..3, how many output rows would appear before stopping?

A 3

B 5

C 4

D 2

💡 Hint

Refer to variable_tracker and execution_table pattern for number of items processed.

Concept Snapshot

ForEach-Object iterates over each item in a collection.
Use $_ to access the current item.
Run a script block on each item.
Outputs the result for each.
Stops when no items remain.

Full Transcript

ForEach-Object in PowerShell takes each item from a collection one by one. It stores the current item in the special variable $_. Then it runs the code inside the script block on that item. The result is output. This repeats until all items are processed. For example, 1..3 | ForEach-Object { $_ * 2 } doubles each number from 1 to 3, outputting 2, 4, and 6. The variable $_ changes each step to the next item. When no items remain, the iteration stops.