cron job

Hi
I need some help setting a cron job to run a script starting from a given time and running every 30 seconds till the next 2 hours is finished.

You'll need to make 3 cron jobs:

the first will put the second in place at whatever time you choose

the second will be a script that kicks off every minute, runs a command, sleeps for 30 secs, then runs the command again...

the third will get rid of the second...

Hi i would need more details...

So, do you want it written for you? Not to be rude, but the more you put in, the more you get out. For what you asked, I think you got a pretty reasonable response. What the 2nd anonymous suggested will work. If you need more info on Cron jobs, look at this:
http://campuscgi.princeton.edu/man?cron

What is it that the script does? Will it take longer than 30 sec. to complete? Not that this would effect anything, just curious.

to add a cron job:
$> crontab -e
then type in the data...
the "data" is:
|`Min. to be executed
| |`Hour to be executed
| | |`Month to be executed
| | | |`Week day to be executed
| | | |
* * * * <command>
if you want something to run evrey min. it would be:
*/1 * * * /some/program/
to put the output into /dev/null:
*/1 * * * /some/program/ >/dev/null 2>&1