Getting to Know the Debug-Job Cmdlet in PowerShell

Hey PowerShell enthusiasts! 👋

Today on Wahmans PowerShell blog, we’re going to explore a cmdlet that might not be the first one you reach for every day, but it can be a real lifesaver when working with background jobs. I’m talking about Debug-Job.

Description: According to Microsoft, Debug-Job “Debugs a running background, remote, or Windows PowerShell Workflow job.” Essentially, if you’ve kicked off a job in the background and something isn’t working quite right, Debug-Job lets you dig in and figure out what’s going wrong – without stopping the entire script.

Let’s break this down with some practical examples, starting from the basics and building up to more advanced usage. 💪

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🔰 Example 1: Starting Simple — Debugging a Background Job

This example covers running a simple command as a background job and debugging it while it runs.

Start-Job -ScriptBlock {
    Start-Sleep -Seconds 10
    "Finished Sleeping"
} -Name SleepJob

# Get the job and debug it
$job = Get-Job -Name SleepJob
Debug-Job -Job $job

When you use Debug-Job here, PowerShell attaches a debugger session to the active job so you can see what’s going on as it processes.

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🚶 Example 2: Using Breakpoints in a Job

Let’s say we want to hit a breakpoint within a background job. This helps you debug specific code paths inside the job.

# Create a script block with a conditional breakpoint
$scriptBlock = {
    $x = 0
    while ($true) {
        if ($x -eq 5) { $breakpoint = 1 } 
        $x++
        Start-Sleep -Milliseconds 500
    }
}

Start-Job -ScriptBlock $scriptBlock -Name LoopJob
$job = Get-Job -Name LoopJob
Debug-Job -Job $job

Inside the debug session, you can step through code, inspect variables, and see where logic might go awry. The loop simulates a more realistic process that may need investigation.

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🚀 Example 3: Debugging a Remote Job

Imagine initiating a remote job on another machine and needing to troubleshoot it remotely. Here’s how that might look (note: this requires remoting to be set up and permitted):

$remoteSession = New-PSSession -ComputerName "RemoteServer"

Start-Job -ScriptBlock {
    Get-Process
} -Name ProcessJob -RunAs32 -Session $remoteSession

$remoteJob = Get-Job -Name ProcessJob
Debug-Job -Job $remoteJob

Debugging remote jobs lets you inspect behavior on a remote machine without copying or replicating the work locally.

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🏗️ Example 4: Debugging a Complex Workflow Job

Let’s make things more advanced: suppose you have a PowerShell Workflow that performs multiple tasks across workflows. We can use Debug-Job to jump in:

Workflow SampleWorkflow {
    Write-Output "Step 1"
    Start-Sleep -Seconds 3
    Write-Output "Step 2"
    Start-Sleep -Seconds 3
    Write-Output "Completed"
}

$job = Start-Job -ScriptBlock { SampleWorkflow } -Name WorkflowJob
Debug-Job -Job $job

Workflow jobs can have multiple checkpoints and parts, so the ability to examine each stage helps immensely during development or troubleshooting.

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The Debug-Job cmdlet is incredibly valuable when you need more insight into what your background, remote, or workflow jobs are doing. Rather than guessing or adding extra logs, dive into the live execution context and take control!

👉 Pro Tip: When you exit a debug session, PowerShell offers several options like c for continue, or q for quit. Make sure to check those options out to prevent inadvertently stopping your job.

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