The specific question for cron using Dillon's minimalist cron version is:
How to create a cron job that runs every first Friday of the month, in ASYNC mode?
Dillon's cron attempts to mix synchronous cron (the traditional) and asynchronous (anacron style) in a single daemon.
The idea is great, but the execution not so much, as one needs to read attentively what makes a cron entry SYNC or ASYNC. (It would be better just to have a TAG like SYNC and ASYNC in the line, and end this problem, but I diverge).
From what I understand, lines that causes the behavior to be ASYNC are those that uses the formats
@freq ID commandor* * * * * ID FREQ=X command.
Those will create a file at /var/spool/cron/cronstamps.
To create a SYNC entry that runs every first Friday of the month, it would be, for example:
10 5 1 * fri ID=scrubzpool /sbin/zpool scrub tank
And to make this ASYNC, once a month (but not every first Friday), the options would be:
@monthly ID=scrubzpool /sbin/zpool scrub tank
Maybe there is a way to explain month on FREQ= tag, but I'm not sure. The best I could come up with was 4 weeks:
10 5 1 * * ID=scrubzpool FREQ=4w /sbin/zpool scrub tank
The github code is here, but with special relation to this question is the file database.c , function ParseInterval, line 677.
I cannot find any explanation on how to mix FREQ= with traditional cron entry to achieve every first Friday of the month.
I wonder if this is correct:
10 5 1 * fri ID=scrubzpool FREQ=4w /sbin/zpool scrub tank
Or something that could create such result.
