Add an option to return the expiration date in unixtime (time since
epoch).
./check_expire -H domain -u
It's particularly useful for alerting or monitoring systems that do
their own calculation based on the metric they receive (and not based on
exit codes).
For instance you can use the following in zabbix 5.4:
- item: check_expire["-H","{HOST.CONN}","-u"]
- trigger: last(/check_expire["-H","{HOST.CONN}","-u"])-now()<2592000
Where 2592000 is 30 days in seconds.
