Question 1

What is a cron expression?

Accepted Answer

A cron expression is a string of five fields (minute, hour, day-of-month, month, day-of-week) that defines a recurring schedule. It's used by Unix/Linux cron daemons, CI/CD pipelines, cloud schedulers, and many automation tools.

Question 2

What does * mean in cron?

Accepted Answer

The asterisk (*) means 'every' — it matches all possible values for that field. For example, * in the hour field means 'every hour'.

Question 3

What is the difference between / and - in cron?

Accepted Answer

The slash (/) means 'every N' — for example, */5 in minutes means every 5 minutes. The dash (-) defines a range — 1-5 in day-of-week means Monday through Friday.

Question 4

How do I run a cron job at midnight?

Accepted Answer

Use '0 0 * * *' — minute 0, hour 0, every day of month, every month, every day of week. This runs at 00:00 (midnight) every day.

Question 5

Does this tool support seconds or years?

Accepted Answer

This tool supports standard 5-field cron expressions (minute, hour, day-of-month, month, day-of-week). Some systems like Quartz add seconds and year fields, which are not covered here.

Crontab Explainer

Cron Syntax

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