┌───────────── minute (0-59)
│ ┌───────────── hour (0-23)
│ │ ┌───────────── day of month (1-31)
│ │ │ ┌───────────── month (1-12)
│ │ │ │ ┌───────────── day of week (0-6, Sun=0)
│ │ │ │ │
* * * * *  command
Special characters:
*    = every value
,    = list (1,3,5)
-    = range (1-5)
/    = step (*/5 = every 5)

# Every minute
* * * * *
Every 5 minutes
*/5 * * * *
Every 15 minutes
*/15 * * * *
Every 30 minutes
*/30 * * * *
Every hour (at minute 0)
0 * * * *
Every day at midnight
0 0 * * *
Every day at 6am
0 6 * * *
Every day at 6am and 6pm
0 6,18 * * *

# Every Monday at 9am
0 9 * * 1
Every weekday at 9am (Mon-Fri)
0 9 * * 1-5
Every weekend at 10am (Sat-Sun)
0 10 * * 0,6
First day of every month at midnight
0 0 1 * *
Every quarter (Jan, Apr, Jul, Oct) on the 1st
0 0 1 1,4,7,10 *
Every year on Jan 1st at midnight
0 0 1 1 *

# Every 10 min during business hours (9am-5pm, Mon-Fri)
*/10 9-17 * * 1-5
Every hour during business hours
0 9-17 * * 1-5
Twice a day (9am and 5pm)
0 9,17 * * *
Every 30 min from 8am to 6pm
*/30 8-18 * * *

# Edit your crontab
crontab -e
List your crontab
crontab -l
Remove your crontab (careful!)
crontab -r
Edit another user’s crontab (root)
sudo crontab -u username -e
Crontab file format:
SHELL=/bin/bash
PATH=/usr/local/bin:/usr/bin:/bin
MAILTO=you@example.com

m h dom mon dow command
0 6 * * * /home/user/backup.sh

# Always use full paths in cron
0 6 * * * /usr/bin/python3 /home/user/script.py
Redirect output to a log
0 6 * * * /home/user/backup.sh >> /var/log/backup.log 2>&1
Suppress all output
0 6 * * * /home/user/script.sh > /dev/null 2>&1
Set environment variables
SHELL=/bin/bash
PATH=/usr/local/bin:/usr/bin:/bin
NODE_ENV=production
Cron uses a minimal PATH — always specify full paths
or set PATH at the top of your crontab

@reboot    /home/user/startup.sh    # Run once at boot
@yearly    /home/user/annual.sh     # 0 0 1 1 *
@monthly   /home/user/monthly.sh    # 0 0 1 * *
@weekly    /home/user/weekly.sh     # 0 0 * * 0
@daily     /home/user/daily.sh      # 0 0 * * *
@hourly    /home/user/hourly.sh     # 0 * * * *

Not all cron implementations support these. Standard 5-field syntax always works.