The five fields of a POSIX cron expression
Read minute, hour, day of month, month and day of week with exact numeric bounds.
ReadCron rules explained
Five-field cron without hidden dialect changes
Understand fields, day semantics and intentionally unsupported extensions.
Cron day-of-month and day-of-week OR semantics
See why 0 12 15 * 1 can match the 15th or a Monday.
ReadCron syntax intentionally not supported by CronParse
Steps, names, macros and vendor extensions are rejected rather than guessed.
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