Windows – How to prevent a scheduled task from running if the same task is already running

scheduled-taskschedulingscriptingwindowswindows-xp

I have written a php script to check if there are any new files in a folder and, if any new files exist, upload them to a server. These files can be quite large. I want to run this script frequently-let's say every 5 min-as a scheduled task so that the files get moved to the server as soon as possible. However, once the script is already attempting to upload a file, I do not want it to be run again, as I am afraid the second instance will overwrite the file that is already being uploaded to the server.

How can I run the script as a scheduled task unless the script is already running?

Best Answer

Assuming you're just setting the task to "Repeat" in the XP "Scheduled Tasks" system, no further action on your part is needed. Scheduled Tasks won't "Repeat" a task if it's already running.

If you want to override that default, you can check the box "If the task is still running, stop it at this time" to cause the task scheduler to kill the last instance before starting a new one (though it sounds like you probably don't want that).

Related Solutions

How to Run a .bat File in a Scheduled Task Without a Window

You could run it silently using a Windows Script file instead. The Run Method allows you running a script in invisible mode. Create a .vbs file like this one

Dim WinScriptHost
Set WinScriptHost = CreateObject("WScript.Shell")
WinScriptHost.Run Chr(34) & "C:\Scheduled Jobs\mybat.bat" & Chr(34), 0
Set WinScriptHost = Nothing

and schedule it. The second argument in this example sets the window style. 0 means "hide the window."

Complete syntax of the Run method:

 object.Run(strCommand, [intWindowStyle], [bWaitOnReturn])

Arguments:

object: WshShell object.
strCommand: String value indicating the command line you want to run. You must include any parameters you want to pass to the executable file.
intWindowStyle: Optional. Integer value indicating the appearance of the program's window. Note that not all programs make use of this information.
bWaitOnReturn: Optional. Boolean value indicating whether the script should wait for the program to finish executing before continuing to the next statement in your script. If set to true, script execution halts until the program finishes, and Run returns any error code returned by the program. If set to false (the default), the Run method returns immediately after starting the program, automatically returning 0 (not to be interpreted as an error code).

Cron – How to Prevent Duplicate Cron Jobs Running

There are a couple of programs that automate this feature, take away the annoyance and potential bugs from doing this yourself, and avoid the stale lock problem by using flock behind the scenes, too (which is a risk if you're just using touch). I've used lockrun and lckdo in the past, but now there's flock(1) (in newish versions of util-linux) which is great. It's really easy to use:

* * * * * /usr/bin/flock -n /tmp/fcj.lockfile /usr/local/bin/frequent_cron_job

Best Answer

Related Solutions

How to Run a .bat File in a Scheduled Task Without a Window

Cron – How to Prevent Duplicate Cron Jobs Running

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