Measure CPU utilization

cpu.clj

(defn- cpu-stats
  "Returns measures of the various types of CPU usage to date"
  []
  (->> (-> (clojure.java.shell/sh "cat" "/proc/stat")
           :out
           (clojure.string/split #"\n")
           first
           (clojure.string/split #"\s"))
       (remove clojure.string/blank?)
       (drop 1)
       (map #(Integer/parseInt %))))

(defn start-cpu-meter
  "Create and return a new CPU meter, an opaque data structure meant
  only to be passed to `sample-cpu-meter`."
  []
  (cpu-stats))

(defn sample-cpu-meter
  "Returns a floating point number between 0 and 1 representing CPU
  utilization between the time `meter` was started and the call to
  this function."
  [meter]
  (let [end-stats (cpu-stats)
        [a b c idle & more] (map - end-stats meter)]
    (- 1.0 (/ idle (apply + a b c idle more)))))