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~1 min readCron Expression Parser

Tokenizing a Cron Expression

A standard cron expression is 5 whitespace-separated fields:

*/15  9-17  *  *  1-5      # Every 15 min, 9am-5pm, weekdays
0     0    1  *  *         # Midnight on the 1st of every month
30    14   *  *  0         # 2:30pm on Sundays

Field	Meaning	Range
1	minute	0-59
2	hour	0-23
3	day-of-month	1-31
4	month	1-12 (or JAN-DEC)
5	day-of-week	0-6 (or SUN-SAT, 0=Sunday)

Tokenization is the first step. You split on whitespace, validate the field count, and map textual aliases (JAN -> 1, MON -> 1, etc.). Special values like @hourly, @daily, @weekly should expand to their canonical 5-field form before tokenizing.

Your job: read a cron string and output the 5 normalized field strings, one per line.

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