how about week number?

[h0n3ym4k]

Hi guys,
just wondering if a new field "week number" (in a year scale?i.e. 52 max? or in a month scale?i.e. 5 max? how about February?) could be introduced to crontab? so that many people are asking various "week"-dependent questions would be somewhat easier to solve? e.g. 3rd Monday of every/alternate month...etc

[t8m]

The question is how to introduce that in a backwards compatible way.

[h0n3ym4k]

is it possible to steal the weekday field?
Mon-Sun is weekday 0-52 is week num?

[t8m]

0-7 are valid day of a week numbers.

[h0n3ym4k]

that's why has to steal it
0-7 only means week num and Mon-Sun as weekday spec
should be easy to adapt?
or any system that cannot represent using Mon-Sun?

[rptaylor]

This would also provide a close-enough alternative for running tasks e.g. every 1st/2nd/3rd Wednesday of the month, which AFAICT is not possible with current cron features (except possibly with some weird tricks).

While I understand current cron syntax has gone largely unchanged for a long time and must retain compatibility, perhaps there could be a scheme that can also allow new features to be introduced:

• always accept the "conventional" syntax that always works the same way
• for people wanting to use new features, also allow named arguments (kind of like Python function arguments), something like this:
  minute=5 hour=2 day=* month=* weekday=Sun week=50 root echo hello

The fact that all the fields are logical ANDs except if both day of month and weekday are specified is a counterintuitive exception that can cause confusion (and makes it impossible to do Nth Wednesday of a month) so I would suggest that if a new field is added it should have the usual logical AND behaviour.

Aside from being able to support new features, this would also have the benefit of being more user-friendly and human-comprehensible. If each field is named, the intent is clear and unambiguous, so it would be possible to allow any order of fields and omission of fields ('*' by default), meaning you don't have to memorize or look up the syntax to know the meaning of each field. You could for example write:

• hour=2 minute=5 root echo hi
• month=1 day=1 root echo Happy New Year

[t8m]

@rptaylor Nice idea! That should be implementable in backwards compatible way.

Anybody wants to try this?

[rptaylor]

I'm not a developer per se but I will enthusiastically thumbs up emoji to any implementation attempt.