I think you're looking for the benchmark library (in Ruby's stdlib). To 
quote from the docs:
(...)
     This report shows the user CPU time, system CPU time, the sum of
     the user and system CPU times, and the elapsed real time. The unit
     of time is seconds.
(...)
         require 'benchmark'

         n = 50000
         Benchmark.bm(7) do |x|
           x.report("for:")   { for i in 1..n; a = "1"; end }
           x.report("times:") { n.times do   ; a = "1"; end }
           x.report("upto:")  { 1.upto(n) do ; a = "1"; end }
         end

     The result:

                         user     system      total        real
            for:     1.050000   0.000000   1.050000 (  0.503462)
            times:   1.533333   0.016667   1.550000 (  0.735473)
            upto:    1.500000   0.016667   1.516667 (  0.711239)

Marvin
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