I'd like to run a system command and then stop it after specified  
amount of time (in seconds or milliseconds.)  What's the best way to  
do it?

e.g.

exec("cat /dev/video > test.mpg")

then kill the process after so many minutes, seconds, etc...

Also, if there is a better Ruby way to do this other than "cat", I'm  
all ears...

Thanks.