I was trying to figure a cron for every 30 minutes between 2AM to 4AM?
So the cron run time will be: 2:00 2:30 3:00 3:30 4:00
Every hour will be something like this:
0 2,3,4 * * * command
I'd just write it as two distinct rules:
0,30 2-3 * * * /run/this/command 0 4 * * * /run/this/command
If you're the sort that worries about this sort of thing (I'm not), you can use a conditional to get it onto one line:
0,30 2-4 * * * [[ "$(date +%H%M)" != "0430" ]] && /run/this/command
This will run the command given at 4:30 as well, but not actually call your script unless the time is something other than 4:30.