Question 1

What is a cron expression?

Accepted Answer

This builder uses the five-field Unix cron format: minute hour day-of-month month day-of-week. For example, '0 9 * * 1-5' means 9:00 AM Monday through Friday in the scheduler's time zone. Other platforms use different fields or rules.

Question 2

What do the special characters mean in cron?

Accepted Answer

* means 'every'. / means 'every N' (*/5 = every 5 minutes). , separates multiple values (1,3,5). - defines a range (1-5). ? means 'no specific value' (in Quartz cron). L means 'last' (last day of month). # means 'Nth weekday' (2#3 = 3rd Tuesday).

Question 3

What is the difference between cron and crontab?

Accepted Answer

Cron is the daemon that runs scheduled tasks. Crontab (cron table) is the file that stores the schedule definitions. You edit crontabs with 'crontab -e'. Each line in a crontab is: expression command. For example: '0 * * * * /usr/bin/backup.sh'.

Question 4

How do I schedule a job every 15 minutes?

Accepted Answer

Use '*/15 * * * *' for every 15 minutes. Other examples: '0 * * * *' (hourly), '0 0 * * *' (daily at midnight), '0 9 * * 1' (weekly on Monday at 9am), '0 0 1 * *' (monthly on the 1st).

Question 5

What is the difference between Linux cron and Quartz cron?

Accepted Answer

Unix cron uses five schedule fields. Quartz adds a seconds field; EventBridge Scheduler uses a six-field minute-through-year expression. This builder creates five-field expressions only. Check your target scheduler's syntax before deployment.

Question 6

How do I write a cron expression?

Accepted Answer

A Unix cron expression has five fields: minute, hour, day of month, month, and day of week. Use * for every value, */n for steps, and commas for lists. For example, '*/15 * * * *' is every 15 minutes. This tool helps compose and copy an expression; it does not validate syntax or calculate future runs.

Question 7

What does '*/5 * * * *' mean in cron?

Accepted Answer

'*/5 * * * *' means 'every 5 minutes, every hour, every day.' The */ syntax means 'every n units of this field.' Common patterns: '0 * * * *' = every hour, '0 0 * * *' = daily at midnight, '0 0 * * 0' = weekly on Sunday. The builder above generates the expression from plain-language schedule descriptions.

Cron Generator — Free Online Cron Expression Builder & Explainer

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