PowerShell Basics: Loops

Loops are fundamental to programming and scripting, allowing you to execute repetitive tasks efficiently. PowerShell provides several types of loops, each tailored to different scenarios.

For Loop

The for loop is ideal for iterating a specific number of times. It consists of three parts: initialization, condition, and iteration.

Syntax:

for (<initialization>; <condition>; <iteration>) {
    <code to execute>
}

Example:

# Print numbers from 1 to 5
for ($i = 1; $i -le 5; $i++) {
    Write-Output $i
}

Use Case: When you know the exact number of iterations required.

Foreach Loop

The foreach loop is designed for iterating over collections, such as arrays or hash tables.

Syntax:

foreach ($item in <collection>) {
    <code to execute>
}

Example:

# Iterate through an array
$array = @("apple", "banana", "cherry")
foreach ($fruit in $array) {
    Write-Output $fruit
}

Use Case: When working with items in a collection.

While Loop

The while loop continues to execute as long as a specified condition evaluates to $true.

Syntax:

while (<condition>) {
    <code to execute>
}

Example:

# Print numbers from 1 to 5 using a while loop
$i = 1
while ($i -le 5) {
    Write-Output $i
    $i++
}

Use Case: When the number of iterations depends on a dynamic condition.

Do-While Loop

The do-while loop is similar to the while loop but guarantees that the code block executes at least once.

Syntax:

do {
    <code to execute>
} while (<condition>)

Example:

# Print numbers from 1 to 5 using a do-while loop
$i = 1
do {
    Write-Output $i
    $i++
} while ($i -le 5)

Use Case: When you need the block to execute at least once, regardless of the condition.

Do-Until Loop

The do-until loop is the opposite of the do-while loop. It executes until a condition becomes $true.

Syntax:

do {
    <code to execute>
} until (<condition>)

Example:

# Print numbers from 1 to 5 using a do-until loop
$i = 1
do {
    Write-Output $i
    $i++
} until ($i -gt 5)

Use Case: When you need to iterate until a condition is met.

ForEach-Object Loop

The ForEach-Object loop is used in pipelines to process each item in a collection. This is particularly useful for working with cmdlet outputs.

Syntax:

<collection> | ForEach-Object {
    <code to execute>
}

Example:

# Process items in a pipeline
@(1, 2, 3) | ForEach-Object {
    Write-Output ($_ * 2)
}

Use Case: When working with pipeline data.

Loop Control Statements

PowerShell provides additional statements to control loop execution:

break: Exits the loop immediately. for ($i = 1; $i -le 5; $i++) { if ($i -eq 3) { break } Write-Output $i }
continue: Skips the current iteration and moves to the next one. for ($i = 1; $i -le 5; $i++) { if ($i -eq 3) { continue } Write-Output $i }

Choosing the Right Loop

Choosing the right loop depends on your use case:

Use for when you have a fixed number of iterations.
Use foreach for collections.
Use while or do-while for dynamic conditions.
Use ForEach-Object in pipelines for processing items efficiently.

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