Cron Job Syntax

Basic format
* * * * * command
│ │ │ │ │
│ │ │ │ └─ Day of week (0-7, Sunday = 0 or 7)
│ │ │ └─── Month (1-12)
│ │ └───── Day of month (1-31)
│ └─────── Hour (0-23)
└───────── Minute (0-59)

Special characters
* // Any value
, // Value list separator (1,3,5)
- // Range of values (1-5)
/ // Step values (*/5 = every 5)

Every minute
* * * * * command

Every hour at minute 0
0 * * * * command

Every day at midnight
0 0 * * * command

Every day at 3:30 AM
30 3 * * * command

Every Monday at 9 AM
0 9 * * 1 command

Every 15 minutes
*/15 * * * * command

Every 5 hours
0 */5 * * * command

First day of month at midnight
0 0 1 * * command

Weekdays at 8 AM (Mon-Fri)
0 8 * * 1-5 command

Every Sunday at 2 AM
0 2 * * 0 command

Multiple times per day
0 8,12,17 * * * command

Every 30 minutes between 9 AM - 5 PM
*/30 9-17 * * * command

Every quarter (Jan, Apr, Jul, Oct)
0 0 1 1,4,7,10 * command

Weekends at noon
0 12 * * 6,0 command

Edit crontab
crontab -e

List crontab
crontab -l

Remove crontab
crontab -r

Edit for specific user
sudo crontab -u username -e

Special strings
@reboot command // Run at startup
@hourly command // 0 * * * *
@daily command // 0 0 * * *
@weekly command // 0 0 * * 0
@monthly command // 0 0 1 * *
@yearly command // 0 0 1 1 *

Redirect output
0 0 * * * command >> /var/log/cron.log 2>&1