How do I create a crontab through a script

Question

I need to add a cron job thru a script I run to set up a server. I am currently using Ubuntu. I can use crontab -e but that will open an editor to edit the curr

Answer 1

Well /etc/crontab just an ascii file so the simplest is to just

 echo "*/15 * * * *   root     date" >> /etc/crontab

which will add a job which will email you every 15 mins. Adjust to taste, and test via grep or other means whether the line was already added to make your script idempotent.

On Ubuntu et al, you can also drop files in /etc/cron.* which is easier to do and test for---plus you don't mess with (system) config files such as /etc/crontab.