Well, this is not the right way to do since the kill command should be independent from mplayer. The ; simply separates two linux commands on the same line: this means that the system sleeps 3600 seconds
after mplayer has finished. The same for the && syntax which means that the command is executed only if the previous command terminates with a exit status equal to 0 (
success). Using a single & is slightly different, since in this case the first command runs in background and the subsequent command immediately starts after that.
Regarding your original question, if you're scheduling the mplayer job, you might schedule a killing job one hour later and use
Code:
/usr/bin/pkill -9 mplayer
in the crontab entry. pkill will kill processes based on the command name, not the PID. Maybe this is what you're looking for.