alt Hacker NewsSure, I'll pile on here. To do nontrivial scheduling you'd use the entirely-obvious-and-intuitive syntax described at [0]. For example:
Mon,Fri *-01/2-01,03 *:30:45
[0] <https://www.freedesktop.org/software/systemd/man/latest/syst...>
[1] This question is sarcasm. SystemD is often like this... dead simple things look dead simple, but complex things are -if they're possible at all- at least as complex as they are everywhere else.
Replies
ffaccount2 • yesterday at 12:38 PM
To be honest it looks rather easy to digest? I can sort of guess the meaning without documentation.
For cron, despite years of looking at it, I can never remember what those numbers mean and I need to Google almost every time.
p0358 • last Tuesday at 5:01 PM
If you know the syntax, it's still actually rather trivial. Still easier to read than advanced cron magic.
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I found the systemd time spec syntax you referenced to be logical and well thought out.
Cron syntax is simpler for the easy cases because cron tries to do less. It ignores years and seconds entirely, and doesn't try to adhere roughly to ISO8601 ordering and field separators, instead using space universally for field separation and euro-style least-to-most significant field ordering. I like ISO8601, so I get along with systemd's style better, despite it introducing slightly more cognitive load.
The only thing that threw me for a loop and seems like "special magic" was
> "Mon *-05~07/1" means "the last Monday in May."
But good luck doing that in one line in cron.
Some cron-style libraries seem to support L/W/# for last / nearest-weekday / nth of month, but I don't know if any system crons do. (cronie? dcron? I don't think so. fcron? bcron? I don't see it there either.) '#' is syntactic sugar for DOW + 7-day range, while L is covered by the above quoted syntax.
If your cron has that kind of syntax, then for a case like "weekday closest to 1st of month", "W" is more convenient than writing 3 systemd timer rules to cover the three cases (weekday day 1, monday day 2, friday last day of month), but that's a big if. Generally you'd have to write 3 rules in cron anyway.