Watch Disk Use, CPU, and Load Average via Command Line
Here’s a nice trick if you need to continuously observe your Macs system usage. Attaching this flag to the iostat command you’ll get a constant stream of updated load information:
You’ll then get a continuously updated stream of your hard disk usage, CPU split into user/system/idle, and your Macs load average:
iostat will keep running in this mode until you stop it with Control+C to halt it. You can also just run iostat on it’s own and it’ll spit out a one-off look at the system stats, or you can just use the top command for similar effect.
If mucking around in the command line isn’t your thing, you can get most of this information from the activity monitor, which functions as a task manager of sorts for Mac OS X but also details system usage information.