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diff --git a/docs/gcron.md b/docs/gcron.md new file mode 100644 index 0000000..4327083 --- /dev/null +++ b/docs/gcron.md @@ -0,0 +1,62 @@ +# Gcron + +Gcron is a small daemon that executes batch commands once a certain +condition is met. + +In a typical installation, it reads configuration files from `/etc/gcron.d`. +If used together with the init system in this package, the `service` command +can be used to administer symlinks in that directory, pointing +to `/usr/share/init/<name>.gcron`. + +Each file in the configuration directory represents a single scheduled batch +job. The syntax and most of the keywords are similar to `initd` service files +(See [services.md](services.md)). + +## Cron Style Patterns + +The following keywords can be used to specify classic cron style patterns for +when a job should be run: + + * `hour` + * `minute` + * `dayofmonth` + * `dayofweek` + * `month` + +For each of those keywords, a comma separated sequence of times can be +specified. Time ranges can be specified using the syntax `<start>-<end>`, +or using `*` for every possible value. A sequence (either range or star) +can be suffixed with `/<step>` to specify an increment. +For instance, `minute */5` means every five minutes and `minute 15-30/2` +means every two minutes between quarter past and half past. + +In addition to numeric values, the keywords `dayofweek` and `month` allow +specifying 3 letter, uppercase week day and moth names such as `MON`, `TUE`, +etc and `JAN`, `FEB`, ... + +The job is only run when all specified conditions are met. Omitting a field +is the same as specifying `*`. + +## Named Intervals + +Alternatively to the above, the keyword `interval` can be used. The following +intervals can be specified: + + * `yearly` or `annually` means on every January the first at midnight. + * `monthly` means on every first of the month at midnight. + * `weekly` means every Sunday at midnight. + * `daily` means every day at midnight. + * `hourly` means every first minute of the hour. + +## Command Specification + +To specify *what* should be done once the condition is met, the following +keywords can be used: + + * `exec` - the command to run. Multiple commands can be grouped + using curly braces. + * `user` - a user name or ID to set before running the commands. + * `group` - a group name or ID to set before running the commands. + * `tty` - similar to init service files, the controlling tty or output file + for the batch commands. Like init service files, the `truncate` keyword + can be used. |