You will have to log out and log back in to have this take effect. This will make a crontab for you that is a copy of the system's crontab. Notice that crontab is both the name of the file and an executable program - similar to passwd. Each line in the crontab runs one program. Ranges of numbers are allowed.
Ranges are two numbers separated with a hyphen.
The specified range is inclu- sive. Lists are allowed. Step values can be used in conjunction with ranges. Ranges or lists of names are not allowed. And it should email root after completion of the task telling root what happened.