PowerShell For Loop With Index and Range Examples

In the previous tutorial, we discussed the PowerShell for loop. Now, I will show you some more advanced examples, known as PowerShell for loop with index and range examples.

In this tutorial, I will show you some practical examples of using for loops with indexes and ranges in PowerShell, along with various techniques I’ve learned over the years.

Table of Contents

Basic For Loop Syntax in PowerShell

The for loop in PowerShell follows a similar structure to many other programming languages:

for (initialization; condition; increment) {
    # Code to execute
}

Let’s break this down:

Initialization: Sets up your counter variable (typically $i)
Condition: Evaluates before each loop iteration
Increment: Executes after each loop iteration

Here’s a simple example that counts from 1 to 5:

for ($i = 1; $i -le 5; $i++) {
    Write-Output "Current count: $i"
}

Check out PowerShell ForEach

Iterate Through Arrays Using Index

One of the most common uses of for loops with indexes is to iterate through arrays. This gives you more control than foreach loops because you have access to the position of each element.

$states = "California", "Texas", "Florida", "New York", "Pennsylvania"

for ($i = 0; $i -lt $states.Count; $i++) {
    Write-Output "State #$($i+1): $($states[$i])"
}

The output shows each state with its position:

State #1: California
State #2: Texas
State #3: Florida
State #4: New York
State #5: Pennsylvania

Here is the exact output in the screenshot below:

powershell for loop with index and range

Check out Concatenate Strings Inside Loops in PowerShell

Working with Ranges in PowerShell

PowerShell makes it easy to create ranges using the range operator (..). This is particularly useful when you need to iterate through a specific range of numbers.

# Create a range from 1 to 10
$range = 1..10

for ($i = 0; $i -lt $range.Count; $i++) {
    Write-Output "The square of $($range[$i]) is $([Math]::Pow($range[$i], 2))"
}

Here is the exact output in the screenshot below:

powershell for loop with index and range example

Process Array Elements in Reverse Order

Sometimes you need to process elements in reverse order. Here’s how to do it with a for loop:

$months = "January", "February", "March", "April", "May"

for ($i = $months.Count - 1; $i -ge 0; $i--) {
    Write-Output "Month in reverse order: $($months[$i])"
}

Step Through Arrays with Custom Increments

You’re not limited to incrementing by 1. Here’s an example where we step through an array by 2:

$numbers = 1..20

for ($i = 0; $i -lt $numbers.Count; $i += 2) {
    Write-Output "Every other number: $($numbers[$i])"
}

Read Multiple Conditions in Do-While Loop in PowerShell

Using For Loops with Ranges for Data Processing

Let’s look at a more practical example. Imagine we have sales data for different quarters and want to calculate quarterly averages:

$quarterlySales = @(
    @(15000, 17500, 14200),  # Q1 sales (Jan, Feb, Mar)
    @(18200, 19500, 17800),  # Q2 sales (Apr, May, Jun)
    @(12500, 13800, 15200),  # Q3 sales (Jul, Aug, Sep)
    @(21500, 22800, 24700)   # Q4 sales (Oct, Nov, Dec)
)

for ($q = 0; $q -lt $quarterlySales.Count; $q++) {
    $quarterData = $quarterlySales[$q]
    $total = 0

    for ($m = 0; $m -lt $quarterData.Count; $m++) {
        $total += $quarterData[$m]
    }

    $average = $total / $quarterData.Count
    Write-Output "Quarter $($q+1) average sales: `$$([Math]::Round($average, 2))"
}

Working with String Characters Using Indexes

You can also use for loops to process individual characters in strings:

$sentence = "PowerShell is awesome!"

for ($i = 0; $i -lt $sentence.Length; $i++) {
    if ($sentence[$i] -match '[aeiou]') {
        Write-Output "Vowel found at position $i: $($sentence[$i])"
    }
}

Read PowerShell ForEach Loop

Using For Loops with Dynamic Ranges

Sometimes, you need to work with ranges that are determined at runtime:

function Process-DateRange {
    param (
        [DateTime]$startDate,
        [DateTime]$endDate
    )

    $days = ($endDate - $startDate).Days

    for ($i = 0; $i -le $days; $i++) {
        $currentDate = $startDate.AddDays($i)
        Write-Output "Processing data for: $($currentDate.ToString('MM/dd/yyyy'))"
    }
}

# Example: Process the first week of May 2023
Process-DateRange -startDate "05/01/2023" -endDate "05/07/2023"

Check out While Loop in PowerShell

Create a Loop with Index for CSV Processing

Here’s a practical example that processes a CSV file using indexes:

$csvData = Import-Csv -Path "C:\Data\sales_records.csv"

for ($i = 0; $i -lt $csvData.Count; $i++) {
    $record = $csvData[$i]

    # Skip processing for certain records based on index
    if ($i % 10 -eq 0) {
        Write-Output "Milestone record $i: $($record.ProductName), Sales: $($record.Amount)"
    }

    # Example of updating records based on index
    if ($i -lt 5) {
        $record.Category = "Premium-" + $record.Category
    }
}

Using For Loop with Break and Continue

For loops also support flow control with break and continue:

$temperatures = 68, 72, 65, 83, 90, 92, 87, 71, 78, 74

for ($i = 0; $i -lt $temperatures.Count; $i++) {
    # Skip temperatures below 70
    if ($temperatures[$i] -lt 70) {
        Write-Output "Skipping day $($i+1): $($temperatures[$i])°F (too cool)"
        continue
    }

    # Stop processing if we find a temperature above 90
    if ($temperatures[$i] -gt 90) {
        Write-Output "Alert on day $($i+1): $($temperatures[$i])°F (too hot)"
        break
    }

    Write-Output "Day $($i+1): $($temperatures[$i])°F (comfortable)"
}

Read PowerShell Do While Loop

Working with Multiple Arrays Simultaneously

You can use indexes to work with multiple arrays in parallel:

$products = "Laptop", "Phone", "Tablet", "Monitor", "Keyboard"
$prices = 1200, 800, 350, 250, 80
$inventory = 15, 28, 32, 10, 45

for ($i = 0; $i -lt $products.Count; $i++) {
    $totalValue = $prices[$i] * $inventory[$i]
    Write-Output "Product: $($products[$i]) | Price: $($prices[$i]) | Inventory: $($inventory[$i]) | Total Value: $totalValue"
}

PowerShell for loops with indexes and ranges are beneficial. Whether you’re processing arrays, iterating through specific ranges, or need precise control over loop execution, the for loop can be used.

I hope you now learn everything about PowerShell for loops with indexes and ranges examples. If you have any questions or want to share how you use for loops in your projects, I’d love to hear from you in the comments below!