Cron schedule syntax #

The Vieter cron daemon uses a subset of the cron expression syntax to schedule builds.

Format #

a b c d

• a: minutes
• b: hours
• c: days
• d: months

An expression consists of two to four sections. If less than four sections are provided, the parser will append * until there are four sections. This means that 0 3 is the same as 0 3 * *.

Each section consists of one or more parts, separated by a comma. Each of these parts, in turn, can be one of the following (any letters are integers):

• *: allow all possible values.
• a: only this value is allowed.
• */n: allow every n-th value.
• a/n: allow every n-th value, starting at a in the list.
• a-b: allow every value between a and b, bounds included.
• a-b/n: allow every n-th value inside the list of values between a and b, bounds included.

Each section can consist of as many of these parts as necessary.

Examples #

• 0 3: every day at 03:00AM.
• 0 0 */7: every 7th day of the month, at midnight.

CLI tool #

The Vieter binary contains a command that shows you the next matching times for a given expression. This can be useful for understanding the syntax. For more information, see vieter-schedule(1).