如何从计划任务中删除触发器

Question

I'm using the Task Scheduler cmdlet in PowerShell to configure triggers for a scheduled task of a Perfmon Data Collector set. I'm using the following to modify the Scheduled task and start the data collector set when the server starts:

$trigger = New-ScheduledTaskTrigger -AtStartup
Set-ScheduledTask -TaskPath '\Microsoft\Windows\PLA\' -Taskname $TemplateName -Trigger $trigger

But I want to know if there is a way of removing this trigger from the scheduled task config. I don't want to disable the Scheduled task, just want to remove this trigger from the Scheduled Task.

Doesn't look like there is a way of doing that from the PowerShell cmdlets. Any help will be appreciated.

Answer 1

There doesn't appear to be a PowerShell cmdlet to delete a trigger, but you can do it through the Schedule.Service COM object. The following example will remove the first trigger from the task named MyTask.

You may need to add a loop to inspect the triggers in order to find the specific trigger you want to remove based on the start time or other criteria.

Note: The trigger enumerations are one-based, not zero-based, so to remove the first trigger it is $definition.Triggers.Remove(1)

Credit to Changing Scheduled Tasks with PowerShell for much of this.

$taskName = "MyTask"
$triggerToDelete = 1

# connect to Task Scheduler:
$service = New-Object -ComObject Schedule.Service
$service.Connect($env:COMPUTERNAME)

# pick a specific task in a container:
$folder = $service.GetFolder('\')
$task = $folder.GetTask($taskName)

# get task definition and change it:
$definition = $task.Definition
$definition.Triggers.Remove($triggerToDelete)

# write back changed task definition:
# 4 = Update
$folder.RegisterTaskDefinition($task.Name, $definition, 4, $null, $null, $null)

To specifically delete all triggers that are "AtStartup" triggers, replace the # get task definition and change it: section with the following. Note that it is looping through the triggers backwards, because if one is removed, the IDs of any following triggers change.

# get task definition and change it:
$definition = $task.Definition

$numTriggers = $definition.Triggers.Count

# loop backwards through the triggers and 
# remove any that are "Startup" (Type = 8)
for($triggerId=$numTriggers; $triggerId -gt 0; $triggerId--){
    if($definition.Triggers.Item($triggerId).Type -eq "8"){
        $definition.Triggers.Remove($triggerId)
    }
}

I'm sure this could be done with fewer lines by piping to a where clause, but it always takes me longer to get that right so I just loop through things as long as it's something that will have minimal impact.