from man it said
The execution of files can be allowed or denied by creating file jobs.allow or jobs.deny which worked similar as other allow/deny config files
But the example has something like 0logwatch, what is the 0 means here? where can I find the exact man page of the syntax?
The entries in jobs.allow and jobs.deny are the file names of cron jobs, as defined in for example /etc/cron.d, /etc/cron.daily etc. A given jobs.deny denies the named jobs in the same directory; thus, a 0logwatch entry in /etc/cron.daily/jobs.deny will prevent /etc/cron.daily/0logwatch from running.
This isn’t supported by all versions of cron; notably, cron on Debian derivatives doesn’t support this feature, whereas cron on Fedora derivatives do. If you’re using a Fedora derivative, run man crontabs there to get an up-to-date man page which is easier to understand than the version you found on the Internet.
