cron irregularity
- Planted:
There isn’t just one universal standard for cron expression syntax, as far as I can tell.
I noticed because the widely-used cron
Rust crate (>2M downloads) that we use at Membrane includes a seconds field and handles day of week differently from the syntax I'm used to.
Or maybe there is an agreed-upon standard? The cron Wikipedia page has a section on "Nonstandard predefined scheduling definitions", which implies there are standard predefined scheduling definitions. And from the mcron man pages via gnu.org:
The format of a cron command is very much the V7 standard...The time and date fields are:
Field Allowed values--------------------------------minute 0-59hour 0-23day of month 0-31month 0-12 (or names, see below)day of week 0-7 (0 or 7 is Sun, or use names)
cron tl;dr
cron
is a CLI and job scheduler for Unix-like OSs. crontab
(cron table) files run shell commands on a schedule (colloquially, "cron jobs"). The cron daemon wakes up every minute, reads crontab files, and executes commands as appropriate.
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