get current cpu usage with ruby or cli (NOT live like top)

I want to find a way that I can call a command or method, and get an int with the cpu usage the moment I called it. Not like top, where it keeps refreshing.

I am writing an app in MacRuby, so I can either use a cl command, or some ruby api.

any thoughts?

thanks

edit: can I somehow call top and get one frame o开发者_C百科f it in ruby? and from there I can get the percentage I need. Although I guess this way is not ideal..

kinda SOLVED: top -l 1 on mac, top -n 1 on linux. It runs top for just one frame.

---

The w command gives a output which contains load average in the first line.

So try w | head -1

It's not an int, and not strictly "CPU usage", but it might be a start.

---

Have you checked whether there's a command-line option for top to just give an instantaneous once-only output, and have you looked at ps?