How to create cronjobs

Cron job syntax:
minute(0-59) hour(0-23) dayofmonth(1-31) month(1-12) dayofweek(0(sunday)-6) user commands

Run every minute

* * * * * user command1; command2; ...

Run every 5 minutes

*/5 * * * * user command1; command2; ...

Run every hour from 4 minutes until 10 minutes past the hour

4-10 * * * * user command1; command2; ...

Run every hour from 4 minutes until 10 minutes past the hour, but just every two minutes within this interval

4-10/2 * * * * user command1; command2; ...

Run on Mondays and Wednesdays at 8:30 am

30 8 * * 1,3 user command1; command2; ...

Run every hour, from 4 minutes until 10 minutes past the hour and from 20 minutes until 50 minutes past the hour. Within the first interval every minute, within the second interval every 5 minutes.

4-10,20-50/5 * * * * user command1; command2; ...

Print the cron jobs for the current user

crontab -l

Edit the cron jobs for the current user

crontab -e

Print the cron jobs for a particular user

crontab -u username -l

Edit the cron jobs for a particular user

crontab -u username -e