Linux Cron Expression Guide — Build Cron Jobs With Confidence

Cron is installed on virtually every Linux and macOS machine. If you're managing any server, you'll encounter cron eventually. The expression syntax is compact and slightly cryptic at first glance, but once you understand the five fields, you can write and read cron schedules fluently.

The five fields explained

# ┌───── minute (0-59)
# │ ┌───── hour (0-23)
# │ │ ┌───── day of month (1-31)
# │ │ │ ┌───── month (1-12)
# │ │ │ │ ┌───── day of week (0=Sun, 1=Mon ... 6=Sat)
# │ │ │ │ │
# * * * * * command

Special characters

• * — every unit. * in the hour field means every hour
• , — list separator. 0,30 * * * * runs at minute 0 and minute 30
• - — range. * 9-17 * * * runs every minute between 9 AM and 5 PM
• / — step. */15 * * * * runs every 15 minutes

Common expressions

# Every minute
* * * * *

# Every hour at minute 0
0 * * * *

# Every day at midnight
0 0 * * *

# Every Monday at 9 AM
0 9 * * 1

# First day of every month at noon
0 12 1 * *

# Every 5 minutes
*/5 * * * *

# Weekdays at 8 AM
0 8 * * 1-5

# January 1st at midnight (New Year task)
0 0 1 1 *

Special shorthand strings

Many cron implementations also support convenient aliases:

• @reboot — run once at startup
• @hourly — same as 0 * * * *
• @daily — same as 0 0 * * *
• @weekly — same as 0 0 * * 0
• @monthly — same as 0 0 1 * *

Editing and viewing cron jobs

crontab -e opens your personal crontab for editing. crontab -l lists your current cron jobs. crontab -r removes all your cron jobs (use with care). System-wide cron jobs live in /etc/crontab and /etc/cron.d/.

Use the Cron Generator to build expressions visually and paste them into your crontab without memorizing the syntax.