Get-Event

Exploring the `Get-Event` Cmdlet in PowerShell

Welcome back to Wahmans PowerShell blog! Today, we’re diving into the Get-Event cmdlet, a lesser-known but very useful tool in PowerShell for handling event-driven programming. According to Microsoft Docs, Get-Event “gets the events in the event queue”—essentially, it allows you to inspect events that have been registered and triggered during a PowerShell session. So let’s break it down from beginner to advanced usage with some clear examples.

What is an Event Queue?

When you subscribe to an event using cmdlets like Register-ObjectEvent, any triggered events are stored in a queue until you handle them or inspect them. Get-Event allows you to access this queue to view or process those events.

Use Cases and Examples

Example 1: Get All Events in the Queue (Beginner)

Get-Event

This is the simplest use of Get-Event. If you’ve previously registered any events and those events have fired, this command returns the list of events in the event queue. If the queue is empty, it returns nothing.

Example 2: Subscribing and Listening for a Timer Event (Intermediate)

$timer = New-Object Timers.Timer
$timer.Interval = 2000
$timer.AutoReset = $true
Register-ObjectEvent -InputObject $timer -EventName Elapsed -SourceIdentifier TimerElapsed
$timer.Start()
Start-Sleep -Seconds 5
Get-Event

Here we create a .NET timer and register an event that fires every 2 seconds. We then let the script sleep for 5 seconds, during which at least two events should be triggered and stored. Get-Event retrieves those.

Example 3: Filtering Events by Source Identifier (Intermediate)

Get-Event -SourceIdentifier TimerElapsed

This command filters the events specifically for those fired by an event with the source identifier “TimerElapsed”. This is useful when you’re registering multiple events and only want to inspect specific ones.

Example 4: Handling and Removing Events from the Queue (Advanced)

$events = Get-Event -SourceIdentifier TimerElapsed
foreach ($event in $events) {
    Write-Output "Event triggered at: $($event.TimeGenerated)"
    Remove-Event -EventIdentifier $event.EventIdentifier
}

This example does two things: it processes each event in the queue and then removes them using Remove-Event, preventing duplicate handling. This is critical in production automation where you want to ensure events are handled exactly once.

Wrap-Up

The Get-Event cmdlet is a powerful feature when working with asynchronous PowerShell scripts or custom event handlers. Whether you’re just starting or diving into more complex workflows, it enables you to monitor and debug your event-driven logic easily.

Happy scripting, and I will see you in the next post!

Exploring the Get-Event Cmdlet in PowerShell