crontab(1posix) - schedule periodic background work
-e     Edit  a copy of the invoking user's crontab entry, or create an empty entry to edit if the crontab
       entry does not exist. When editing is complete, the entry shall be installed as the user's crontab
       entry.
-l     (The letter ell.) List the invoking user's crontab entry.
-r     Remove the invoking user's crontab entry.