Cron Format
┌───────── minute (0-59)
│ ┌───────── hour (0-23)
│ │ ┌───────── day of month (1-31)
│ │ │ ┌───────── month (1-12)
│ │ │ │ ┌───────── day of week (0-7, 0=Sun, 7=Sun)
│ │ │ │ │
* * * * *
Special Characters
| Char | Meaning | Example |
|---|
* | Any value | * * * * * = every minute |
, | List | 1,15 * * * * = min 1 and 15 |
- | Range | 1-5 * * * * = min 1 thru 5 |
/ | Step | */15 * * * * = every 15 min |
Common Patterns
| Expression | Description |
|---|
* * * * * | Every minute |
*/5 * * * * | Every 5 minutes |
0 * * * * | Every hour |
0 0 * * * | Every day at midnight |
0 9 * * 1-5 | Weekdays at 9 AM |
0 0 1 * * | First day of every month |
0 0 * * 0 | Every Sunday at midnight |
30 8 * * 1 | Every Monday at 8:30 AM |
0 */6 * * * | Every 6 hours |
0 0 1 1 * | January 1st at midnight |
Crontab Commands
crontab -e # Edit crontab
crontab -l # List crontab
crontab -r # Remove all cron jobs
# Example crontab entry
0 2 * * * /path/to/backup.sh >> /var/log/backup.log 2>&1
@-shortcuts (Most Cron Implementations)
| Shortcut | Equivalent |
|---|
@reboot | Run once at startup |
@yearly | 0 0 1 1 * |
@monthly | 0 0 1 * * |
@weekly | 0 0 * * 0 |
@daily | 0 0 * * * |
@hourly | 0 * * * * |
