[Bug 1819369] Re: When specifying minute, hour, day-of-month, month, day-of-week values/ranges, given day-of-month range is *ignored*

[Christian Kastner]

On 10.03.19 21:05, Markus Ueberall wrote:
>   # m h dom mon dow user  command
>   00 05 1-7 1,3,5,7,9,11 SAT      sys-maint       some-task some-option   #host1
>   00 05 8-14 1,3,5,7,9,11 SAT     sys-maint       some-task some-option   #host2
>   00 05 15-21 1,3,5,7,9,11 SAT    sys-maint       some-task some-option   #host3
>   00 05 22-28 1,3,5,7,9,11 SAT    sys-maint       some-task some-option   #host4

> The expectation was that none of the entries is executed in parallel
> at any given point in time due to column three> (day-of-month range)

This frequently occurring mistake is an unfortunate result of the
crontab(5) specification.

Quoting the man page:
> Note: The day of a command's execution can be specified by two fields —
> day of month, and day of week. If both fields are restricted (i.e.,
> aren't *), 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.

In short: it's not dom AND dow, but dom OR dow.

Consequently, your specification of SAT in column 5 trumps your
specification of column 3.

The man page contains an example for how to work around this.

-- 
Christian Kastner


** Changed in: cron (Ubuntu)
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1819369

Title:
  When specifying minute,hour,day-of-month,month,day-of-week
  values/ranges, given day-of-month range is *ignored*

Status in cron package in Ubuntu:
  Invalid

Bug description:
  1) The release of Ubuntu you are using, via 'lsb_release -rd'
  # lsb_release -rd
  Description:    Ubuntu 16.04.6 LTS
  Release:        16.04

  2) The version of the package you are using, via 'apt-cache policy pkgname'
  # apt-cache policy cron
  cron:
    Installed: 3.0pl1-128ubuntu2
    Candidate: 3.0pl1-128ubuntu2
    Version table:
   *** 3.0pl1-128ubuntu2 500
          500 http://de.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
          100 /var/lib/dpkg/status

  3) What you expected to happen
  /etc/crontab contains the following entries (each line lives on a separate host with identical setup, system clocks are in sync):
  # m h dom mon dow user  command
  00 05 1-7 1,3,5,7,9,11 SAT      sys-maint       some-task some-option   #host1
  00 05 8-14 1,3,5,7,9,11 SAT     sys-maint       some-task some-option   #host2
  00 05 15-21 1,3,5,7,9,11 SAT    sys-maint       some-task some-option   #host3
  00 05 22-28 1,3,5,7,9,11 SAT    sys-maint       some-task some-option   #host4

  The expectation was that none of the entries is executed in parallel
  at any given point in time due to column three (day-of-month range).
  (Note: All other (default) entries work as expected, syntax of all
  crontab files has been checked using
  https://code.google.com/archive/p/chkcrontab/wikis/CheckCrontab.wiki)

  4) What happened instead
  Yesterday (Saturday, March 9th), the same script was executed in parallel on all four hosts.

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