[ale] cron entry that runs the 2nd saturday of every month

Fri Aug 26 19:09:15 EDT 2011

Ahh, thanks Mike for the reminder. It was years ago when I last needed
to do anything like this, so I suspect that's some of the thinking
that went behind this limitation.

-Erik-

On Fri, Aug 26, 2011 at 6:45 PM, Michael H. Warfield <mhw at wittsend.com> wrote:
> On Fri, 2011-08-26 at 16:47 -0400, Erik Mathis wrote:
>> I ran into this same issue, and iirc cron uses a AND to compare dates.
>> I ended up running it every Monday and added a wrapper to the script
>> to decide if its the right day to do this function. If not, just exit.
>
> No, there's a gotcha in there.  It uses "AND" to compare time and then
> only one of two particular fields (day of month or day of week) have to
> be true, so that's an OR.  That's a PITA.
>
> From "man 5 crontab":
>
> ==
> Note: The day of a command's execution can be specified in the  follow‐
> ing two fields — 'day of month', and 'day of week'.  If both fields are
> restricted (i.e., do not contain the "*" character), the  command  will
> be run when either field matches the current time.  For example,
> "30  4  1,15 * 5" would cause a command to be run at 4:30 am on the 1st
> and 15th of each month, plus every Friday.
> ==
>
> The exact opposite of what you want.
>
> I actually have a more complex example that would work if it truly WAS
> an AND (and I can think of no useful reason for it being an OR but it
> is).
>
> Real world situation.  I have a meeting to take place to take on the
> Wednesday following the 2nd Tuesday.  Notice that it is NOT the the
> second Wednesday.  One Wednesday out of every 7 will be the third
> Wednesday.  So I would need a Wednesday that's on 9-15 (15 being the 3rd
> Wednesday with 1 and 8 being the first two).  An AND condition would be
> perfect.  Tis not to be.  Thou must script.
>
>> -Erik-
>
> Regards.
> Mike
>
>> On Fri, Aug 26, 2011 at 4:27 PM, Geoffrey Myers
>> <lists at serioustechnology.com> wrote:
>> > Lightner, Jeff wrote:
>> >> But the OP wanted 2nd Saturday only.  The +%u just tells you it is
>> >> Saturday - not which Saturday.
>> >
>> > I am the op.  Using the combination of the day of the week and the day
>> > of the month you can calculate whether its the 2nd Saturday of the month
>> > or not.
>> >
>> >>
>> >> I had tested for it being Saturday in my 2008 script but if the cron
>> >> job only runs on Saturday it isn't really necessary.   (My test was
>> >> to prevent someone from just moving the cron job without
>> >> understanding its purpose.)
>> >>
>> >> -----Original Message----- From: ale-bounces at ale.org
>> >> [mailto:ale-bounces at ale.org] On Behalf Of Geoffrey Myers Sent:
>> >> Friday, August 26, 2011 3:39 PM To: Atlanta Linux Enthusiasts
>> >> Subject: Re: [ale] cron entry that runs the 2nd saturday of every
>> >> month
>> >>
>> >> Lightner, Jeff wrote:
>> >>> When I had to do this back in 2008 on HP-UX I worked out a script
>> >>> that relied on the cal (calendar) command.
>> >>>
>> >>> The following command line will give you the 2nd Saturday of the
>> >>> month:
>> >>>
>> >>> cal |cut -c19-20 |grep '[0-9]'|head -2 |tail -1
>> >>>
>> >>> The following command will give you today's day of month: date +%d
>> >>
>> >> Doing something similar only relying on date alone:
>> >>
>> >> date +%d date +%u
>> >>
>> >>> You put your script to compare day of month with the output of the
>> >>> cal line and run the desired command if they match.   Then your
>> >>> cron entry runs EVERY Saturday and the script determines whether to
>> >>> run the commands you want based on whether it is the 2nd Saturday.
>> >>>
>> >>> There may be easier ways to do this on Linux but I figured I'd send
>> >>>  you this at least as a basis for thought.
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>> -----Original Message----- From: ale-bounces at ale.org
>> >>> [mailto:ale-bounces at ale.org] On Behalf Of Geoffrey Myers Sent:
>> >>> Friday, August 26, 2011 2:26 PM To: Atlanta Linux Enthusiasts
>> >>> Subject: [ale] cron entry that runs the 2nd saturday of every month
>> >>>
>> >>>
>> >>> Is it possible?
>> >>>
>> >>> -- Until later, Geoffrey
>> >>>
>> >>> "I predict future happiness for America if they can prevent the
>> >>> government from wasting the labors of the people under the pretense
>> >>>  of taking care of them." - Thomas Jefferson
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>> >>>
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>> >
>> >
>> > --
>> > Until later, Geoffrey
>> >
>> > "I predict future happiness for America if they can prevent
>> > the government from wasting the labors of the people under
>> > the pretense of taking care of them."
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> --
> Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
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