Interpretation of cron - easy points

[OFC_EDM]

Here's my interpretation of some cron settings:

0 3 28 10 5
Run at 3 AM every Friday or 28th day of October.

0 3 25 10 2
Run at 3 AM every Tuesday or 25th day of October.

00 03 08 11 2
Run at 3 AM every Tuesday or 8th day of November.

Am I correct?

[Patrick Wallek]

No, you aren't correct.

0 3 28 10 5
Will run your command on Oct. 28 AND every Friday.

0 3 25 10 2
will run your command on Oct. 25 AND every Tuesday.

00 03 08 11 2
Will run your command on Nov. 8 AND every Tuesday.

The values are cumulative. Have a look at 'man crontab' for more information.

[A. Clay Stephenson]

Yes, in this context the monthdays and the weekdays logical OR rather than logical AND.

[A. Clay Stephenson]

I suppose one should be careful here not to confuse English "or" with Logical "OR". In any event, if either condition is satisfied (e.g. Oct. 28th OR Friday) the command will run. The common mistake is to assume that both conditions must be satisfied (Logical AND) when only one condition (Logical OR) must be satisfied.

[Patrick Wallek]

Kevin,

Sorry I slightly misread your interpretations the first time around. Yes you are correct. I somehow originally saw it without the 'or' separating your week days and dates.

[OFC_EDM]

I've confused myself..


Let's take:

0 3 25 10 2
Run at 3 AM every Tuesday or 25th day of October.

In my wording above some people think it includes Tuesdays outside of October as well. Which is not what I meant.

So that begs the question...will it run on Tuesdays in months other than October?

[Patrick Wallek]

A crontab with '0 3 25 10 2':

will run on Oct. 25 AND EVERY TUESDAY.

Basically if the day is Tuesday, the job runs. OR if the date is Oct. 25, the job runs.

It doesn't matter if the Tuesday is in Oct., Nov., Dec., or whatever. It'll run every Tuesday.

[Jeff_Traigle · Accepted solution]

On that one...

Only on the Tuesdays in October or on the 25th of October

The others would similarly be restricted by the month of the year configuration.

[OFC_EDM]

Interesting. But at least you're all thinking what I'm thinking and I've passed the sanity check.

However I have the jobs setup with those cron settings but they fail to run on the weekday specified (Tuesday or Friday).

Any suggestions on where to start troubleshooting this?

[A. Clay Stephenson]

Rather than adding to the confusion by listing a crontab specification, why don't you state in English when you want this job to be run and then let someone suggest the crontab entry(s) to accomplish this.

[OFC_EDM]

I'm listing the crontab entry because I'm trouble shooting an existing crontab entry for a user who's not available today.

And I wanted to reverse engineer the problem because that usually generates more accurate answers.

But I am in the process of getting a description from the user of when they want the jobs run. Will post when available.

Thanks

[OFC_EDM]

Looks like the user just wanted to run a job on a specific date.

So I told them to take out the "day of week".

Example

00 03 08 11 *
To run the job ONLY on November 8th.

When she used
00 03 08 11 2
It would run everyt Tuesday as well which is not what she wanted.

That works right?

[A. Clay Stephenson]

Yes, that is a correct approach; however, you should note that cron is intended to execute repetitive tasks. If the intent is to run this task each year then cron is appropriate but if the intent is to run this just one time then "at" is the better choice.

[OFC_EDM]

Easy points I said in the subject.
Sorry it took 2 years to assign them !!

Cheers