Automating Windows Task Scheduler with PowerShell

If you are dealing with Windows Task Scheduler, you will almost certainly benefit from being able to automate tasks using PowerShell. Here are some useful tricks to get you started. We’ll use a scenario where we want to re-create a Task Schedule automatically, which will involve:

Stopping the task if it exists
Removing the task if it exists
Creating the task with the appropriate trigger and action
Updating the task settings
Starting the task

Does the task exist?

The simplest way to check with the task exists in Task Scheduler is to pipe all tasks into a filter. We’ll use two commands for this:

Get-ScheduledTask simply gets all the tasks.
Where-Object allows us to filter the list of tasks, for example by task name.

Here’s the script…

$taskName = 'Example'
$taskExists = Get-ScheduledTask | Where-Object {$_.TaskName -like $taskName }

if($taskExists) {
    Write-Host 'The task exists!'
}

Stopping and deleting the task

We can use our $taskExists condition to run our stop and delete commands. For this we will use these two commands:

Stop-ScheduledTask with our task name will end the task.
Unregister-ScheduledTask deletes the task from Task Scheduler.

Here’s the updated script…

$taskName = 'Example'
$taskExists = Get-ScheduledTask | Where-Object {$_.TaskName -like $taskName }

if($taskExists) {
    Write-Host 'Stopping Task'
    Stop-ScheduledTask -TaskName $taskName

    Write-Host 'Unregistering Task'
    Unregister-ScheduledTask -TaskName $taskName -Confirm:$false
}

Creating the task

Creating the task is a little more involved, because we want to set lots of information. Most commonly, we need a user, a trigger, and an action.

$taskName = 'Example'

$filePath = 'c:\Temp\'
$exePath =  "$filePath\Example.exe"

$user= "NT AUTHORITY\SYSTEM"
$trigger = New-ScheduledTaskTrigger -AtStartup
$action = New-ScheduledTaskAction -Execute $exePath

Register-ScheduledTask `
    -TaskName $taskName `
    -User $user `
    -Action $action `
    -Trigger $trigger `
    -RunLevel Highest -Force

This gives us a pretty boilerplate task that starts when the system starts and does something (calls an executable in our case). You can adjust the trigger to use a schedule by changing -AtStartup to a time-based schedule such as -Daily -At 12:00 to run each day at lunch or something more complex, like -Weekly -WeeksInterval 1 -DaysOfWeek Sunday -At 6am, which almost reads like a sentence.

Update task settings

The example in my head is using startup-based running, and just sits in the background doing stuff as long as the machine is switched on. The default settings for a task will actually mean this task is killed after three hours, so we need to change the settings to let it run infinitely. We can do this by updating the ExecutionTimeLimit, but the example shows you how you can change any of the settings for a task.

$taskName = 'Example'
$task = Get-ScheduledTask -TaskName $taskName
$task.Settings.ExecutionTimeLimit = 'PT0H'
Set-ScheduledTask $task

Start the task

The final step is to kick the task off. For a time-based schedule we could just wait until the schedule fires, but for our startup-based task we would be waiting until the machine restarted. It makes sense to kick it off straight away.

We can use Start-ScheduledTask to run the task.

$taskName = 'Example'
Start-ScheduledTask -TaskName $taskName

Summary

I’ve made each of the code samples stand-alone, but you can combine them all by removing all but the first task name variable: $taskName = 'Example'.

If you have a more complex schedule or settings, you can extend those parts of the example.

By first stopping and removing the task before we re-create it, we can run this script as often as we like knowing we will end up with the correct settings at the end of the process. This means we can use it as part of a deployment pipeline, for example.

Written by Steve Fenton on 2nd November 2021

powershell