Crontab (/etc/crontab) structure:
# Example of job definition:
# .---------------- minute (0 - 59)
# | .------------- hour (0 - 23)
# | | .---------- day of month (1 - 31)
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * user-name command to be executedNote that after the timings, a username just be specified as that file is not user-specific
If you do crontab -e you will be editing a crontab just for your current user and therefore don't specify a username before the command
Timings
0 * * * * command # Run command every hour
*/5 * * * * command # Run command every 5 mins
*/30 * * * * command # Run command every 30 mins