Scheduling via cron

(Chuck Pearce) #1

I am having an issue getting a scheduled cron job to run that is for a specific time on a day of the week.

My cron job looks like: “44 14 * * 4 ?”

This should be 44min after 2pm on Thursday however I can not seem to get it to execute ever. I attempted to apply my EDT -4 modification to “44 10 * * 4 ?” but that had no effect either. I can see in the log that the scheduling is being created . Any assistance would be greatly appreciated.

I reviewed some of the suggested replies on the forum but they are from 2013 and appear to be less than helpful.

(C Chen) #2

I think this should work: "0 44 14 * * 5 ?"
Here is the syntax

(Chuck Pearce) #3


That string provided me an invalid string error.

I then tried a few direct examples from that website dealing with days of week including “0 15 10 ? * MON-FRI” and also got invalid errors. Perhaps the implementation in ST is lacking on day of week support? I really didn’t want to make a poller that checks the current day of the week since cron jobs are superior and require less overhead. I even tried replacing MON-FRI with 1-5 or just a numerical day representation and had the same result.

All my other schedulers run just fine it is the one that is specific for a day of the week.

Basically I am working on an Irrigation app and need to say start watering at X time on Y days of the week.

(C Chen) #4

Perhaps the implementation in ST is lacking on day of week support

Perhaps. I seem to remember someone had the same trouble. I have never used day of week myself so can’t say for sure.


The docs refer to some schedule examples:

And just in case…there is a SmartThings limitation of only 4 scheduled jobs per smart app that can be hard to debug if you aren’t looking for it:

To prevent any one SmartApp or device-type handler from using too many resources, only four jobs may be scheduled for future execution at any time.

(Chuck Pearce) #6

It doesn’t appear that any of the advance examples dealing with data after the ? field are working. I have instead created a function that checks the current time/date then schedules the next day to water the plants from that date as a single scheduled date. The recurring days-of-week either silently fail or reject as a valid cron statement.


@Jim ? Sounds like the doc for this section may be out of date. (Ironic.)

(Jim Anderson) #8

I am looking into it.

Platform Update - Release Notes - 03/23/2015
(Matt Nohr) #9

I think you’ve uncovered a bug in how we handle the day-of-week field with cron expressions.

For this specific case, to run at 2:44pm on Thursdays, you should be able to do:

'0 44 14 ? * 5'

The values here are:

  • 0 - seconds
  • 44 - minutes
  • 14 - hour (2pm)
  • ? - day-of-month, which should be ? if you are specifying day-of-week
      • month (all months in this case)
  • 5 - numerical value for Thursday (1 is Sunday)

Now, to make it easier, you should be able to replace that 5 with THU like this '0 44 14 ? * THU', but that is broken.

I am a little surprised that it was failing, but clearly it is. Some expressions work that use strings, like if you want to specify months, you could do '0 44 14 * JUN-AUG ?' and I think it would work. So it isn’t just that using string names are breaking it. Using ranges for the day-of-week is failing too, so it is something with that specific field. For example, this won’t work either '0 44 14 ? * 2-6' (which would be MON-FRI). Basically we try to validate if the expression is a valid cron, and our validation isn’t currently correct. I’m looking into it now.

(Chuck Pearce) #10

@matthewnohr thank you very much for getting back to me on this. I had tried converting the strings to integers (MON = 1 though) but with a different cron format that you presented here. I will give this a try.

On another note I found creating the “Days” function in the SmartApp to check if it was a valid day worked just as well.

(sidjohn1) #11

Im not sure why you want to hard code the job timing in your app, but here is some code that can get the samething done w/o cron.
You can set any day or days of the week and time. Feel free to tweak.

(Matt Nohr) #12

I identified the problem and submitted a fix. It should be available/fixed next week.

Until then, you can do something like @sidjohn1 shared, which will work well. Or if you want the cron, you can use the numbers 1-7 (1 = Sunday) as the day-of-week part.

Thanks for pointing this out!

(Jim Anderson) #13

This should be fixed now.