What is the difference between cron and crontab?

'Cron' is the system daemon that executes scheduled tasks. 'Crontab' (cron table) is the file where users list their scheduled tasks and commands.

Cron Generator - Crontab Expression Builder & Scheduler (2025)

Understanding Cron Syntax

A standard cron expression consists of five fields separated by spaces. Each field represents a unit of time:

Minute
Hour
Day
Month
Weekday
*
*
*
*
*
0-59
0-23
1-31
1-12
0-6

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Expert Tip: Avoid Midnight Spikes

Running heavy jobs exactly at midnight (0 0 * * *) is a common mistake. If many jobs run at the same time, it can spike server load. Instead, use a random minute like 17 0 * * * to spread the load.

⚠️ Common Mistake: Forgetting About Timezone

Cron runs in the server timezone, NOT your local time. If your server is in UTC and you're in EST, your '9 AM' cron will run at 4 PM local time. Always check your server's timezone first!

Special Characters

* (Asterisk): Matches any value (e.g., every minute).
, (Comma): Lists multiple values (e.g., 1,15,30).
- (Hyphen): Defines a range (e.g., 1-5 for Mon-Fri).
/ (Slash): Specifies steps (e.g., */15 for every 15 minutes).

Reviewed by Mike King, Senior SysAdmin

Updated November 26, 2025

Frequently Asked Questions

What is a Cron Expression?

A cron expression is a string of 5 fields separated by spaces that represents a time schedule. The fields are: Minute (0-59), Hour (0-23), Day of Month (1-31), Month (1-12), and Day of Week (0-6, where 0 is Sunday).

How do I run a cron job every 5 minutes?

Use the expression */5 * * * *. The */5 in the minute field means "every 5 minutes".

What does '*' mean in cron?

The asterisk (*) is a wildcard that means "every". For example, * in the hour field means "every hour".

How do I schedule a job for 2 AM every day?

Use the expression 0 2 * * *. This sets the minute to 0 and the hour to 2, running once daily at 2:00 AM.

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