Cron Expression Generator & Parser

Structure of Standard 5-Field Linux Crontab

The traditional Linux crond daemon evaluates cron table entries consisting of five distinct fields separated by white spaces:

• Field 1 (Minute): 0 - 59
• Field 2 (Hour): 0 - 23
• Field 3 (Day of Month): 1 - 31
• Field 4 (Month): 1 - 12 (or JAN-DEC)
• Field 5 (Day of Week): 0 - 6 (0 is Sunday, or SUN-SAT)

Kubernetes CronJob Concurrency Policies

When translating cron expressions into Cloud Native Kubernetes CronJob manifests, pay close attention to the concurrencyPolicy specification:

• Allow (Default): Permits concurrently running job pods if a previous execution hasn't finished.
• Forbid: Skips the new job execution if the previous pod is still active.
• Replace: Cancels the currently running job and replaces it with a new pod.