Now that you’ve written your first .ps1 script, it’s time to move past static commands. This post covers variables, scope, and flow control. The building blocks of decision-making in your scripts. Once you grasp these, you can write logic that adapts to different inputs, environments, or outcomes.

Declaring and Using Variables

Variables in PowerShell always begin with a dollar sign:

$ServiceName = 'wuauserv'

They’re typeless by default but support strong typing when needed:

[string]$ComputerName = 'SRV01'
[int]$RetryCount = 3

Use Write-Output to display a variable’s value during script execution:

Write-Output "Target computer: $ComputerName"

Variables are case-insensitive by default, but write them consistently for readability.

Scope: The Underrated Gotcha

PowerShell has several variable scopes:

  • Global: accessible anywhere (not recommended in scripts)
  • Script: accessible throughout the current script file
  • Local: default inside functions or loops
  • Private: limited to the block in which it’s declared

In most cases, default Local scope is sufficient. But be mindful when working with nested functions or dot-sourcing.

Example:

$global:VMName = 'TestVM'  # Avoid unless absolutely required

Use Write-Output instead of relying on global state to pass data between components.

Conditional Logic: if, elseif, else

Control flow starts with branching. Here’s a simple check for service status:

$service = Get-Service -Name $ServiceName

if ($service.Status -eq 'Running') {
    Write-Output "$ServiceName is running."
}
elseif ($service.Status -eq 'Stopped') {
    Write-Output "$ServiceName is stopped."
}
else {
    Write-Output "$ServiceName is in an unexpected state: $($service.Status)"
}

Keep your conditionals clean and favor -eq, -ne, -gt, -lt, -like, and -match for comparisons. Don’t use ==.

Switch: A Cleaner Alternative

switch blocks simplify multiple matching conditions. They’re basically a bunch of if-statements combined:

switch ($service.Status) {
    'Running' { Write-Output "Service is up." }
    'Stopped' { Write-Output "Service is down." }
    default { Write-Output "Unknown state." }
}

Use switch when comparing one value against multiple known possibilities.

Loops: foreach, while, do-until

foreach

Use foreach when iterating through arrays or collections:

$computers = @('SRV01', 'SRV02', 'SRV03')

foreach ($computer in $computers) {
    Write-Output "Pinging $computer..."
    Test-Connection -ComputerName $computer -Count 1
}

✅ Prefer foreach over ForEach-Object for clarity and performance in scripts.

while and do

Use these for logic that depends on a condition:

$count = 0
while ($count -lt 3) {
    Write-Output "Attempt $count"
    $count++
}

Summary

You now know how to:

  • Declare and use variables
  • Control script flow with if, switch, and loops
  • Avoid scope-related surprises
  • Structure your script’s logic clearly and predictably

This is where your scripts start feeling like real programs—capable of reacting to input, evaluating outcomes, and making decisions.

Coming Up

In Part 3, we’ll introduce functions: how to encapsulate your logic, pass parameters, and build reusable building blocks for clean, modular code.

Until then: Break it down. Use control flow. Keep scripting.