How to Create an On-Demand Scheduled Task Using schtasks.exe Without a Schedule


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When working with Windows Task Scheduler through the command line (schtasks.exe), you might encounter the common error:
Invalid syntax. Mandatory option 'sc' is missing. This occurs because schtasks.exe requires explicit scheduling parameters even for on-demand tasks.


To create a task that runs only when manually triggered (on-demand), you need to specify the scheduling type as ONCE with a far-future trigger date. Here's the proper syntax:

schtasks /create /tn "TestTask" /tr "C:\\path\\to\\program.exe" /sc ONCE /sd 01/01/2099 /st 00:00

This creates:
1. A task named "TestTask"
2. Configured to run just once (ONCE schedule)
3. With a dummy trigger date far in the future (2099)
4. That you can manually run anytime using: schtasks /run /tn "TestTask"


For more complex tasks, you might prefer using an XML definition file:

schtasks /create /tn "AdvancedTask" /xml "task_definition.xml"

Example task_definition.xml content:

<?xml version="1.0" encoding="UTF-16"?>
<Task version="1.2" xmlns="http://schemas.microsoft.com/windows/2004/02/mit/task">
  <RegistrationInfo>
    <Description>Runs my custom script on demand</Description>
  </RegistrationInfo>
  <Triggers /> <!-- Empty triggers section -->
  <Actions Context="Author">
    <Exec>
      <Command>"C:\\scripts\\myscript.bat"</Command>
    </Exec>
  </Actions>
</Task>



    

  • Always run Command Prompt as Administrator when creating system tasks
    • 

  • Use double quotes around paths containing spaces
    • 

  • For PowerShell scripts, specify the PowerShell executable as the program and the script path as argument
    • 

  • Test tasks using schtasks /run /tn "TaskName" before implementing in production
    • 



Here's how to create an on-demand backup task:


schtasks /create /tn "DB_Backup" /tr "powershell.exe -File C:\\scripts\\backup.ps1" /sc ONCE /sd 12/31/2099 /st 23:59


You can then trigger it via:

schtasks /run /tn "DB_Backup"

Or through PowerShell:

Start-ScheduledTask -TaskName "DB_Backup"






When attempting to create a scheduled task in Windows that runs only on-demand (without any predefined schedule), many developers encounter the error:


Invalid syntax. Mandatory option 'sc' is missing.


This occurs because schtasks.exe requires at least a minimal schedule configuration, even for on-demand tasks.


To create a task that runs only when manually triggered, we need to:


schtasks /create /tn "MyOnDemandTask" /tr "C:\path\to\program.exe" /sc ONCE /st 00:00 /f


Key parameters:


    

  • /sc ONCE: Sets a one-time schedule
    • 

  • /st 00:00: Midnight time (arbitrary for our purpose)
    • 

  • /f: Forces creation if task exists
    • 



For more control, use an XML definition file:


<?xml version="1.0" encoding="UTF-16"?>
<Task version="1.2" xmlns="http://schemas.microsoft.com/windows/2004/02/mit/task">
  <RegistrationInfo>
    <Description>On-demand task example</Description>
  </RegistrationInfo>
  <Triggers>
    <RegistrationTrigger>
      <Enabled>false</Enabled>
    </RegistrationTrigger>
  </Triggers>
  <Actions Context="Author">
    <Exec>
      <Command>C:\path\to\program.exe</Command>
    </Exec>
  </Actions>
</Task>


Create task using XML:


schtasks /create /tn "MyOnDemandTask" /xml task.xml


To manually run your task:


schtasks /run /tn "MyOnDemandTask"


For modern systems, PowerShell offers better control:


$action = New-ScheduledTaskAction -Execute "C:\path\to\program.exe"
$trigger = New-ScheduledTaskTrigger -AtStartup -RandomDelay 00:00:00
Register-ScheduledTask -TaskName "MyOnDemandTask" -Action $action -Trigger $trigger -Description "On-demand task"


Disable automatic trigger:


Disable-ScheduledTask -TaskName "MyOnDemandTask"


    

  • Windows requires at least minimal schedule configuration
    • 

  • Using /sc ONCE with arbitrary time is the simplest solution
    • 

  • XML definition provides most flexibility
    • 

  • PowerShell offers more modern and powerful alternatives
    •