Setting up cron job is a very useful feature offered by Linux if you want to automate commands to run at certain time.

# to list current cron jobs running by user.
crontab -l

# to create a new cron job
crontab -u user -e

*Note: I am currently running CentOS 6 and editing /etc/crontab did not work. Also putting a new line after your cron job is required.