Prevent output while using Ruby Benchmark

Question

I'm trying to compare the touch method that Rake includes to shelling out to the system touch.

Each operation is sending output to stdout:

require 'benchmark'
require 'rake'

n = 3
result = Benchmark.bm do |x|
  x.report("sh:") do
    n.times { sh "touch foo.txt" }
  end
  x.report("touch:") do
    n.times { touch "bar.txt" }
  end
end

result:

user     system      total        real
sh:touch foo.txt
touch foo.txt
touch foo.txt
  0.000000   0.010000   0.030000 (  0.024775)
touch:touch bar.txt
touch bar.txt
touch bar.txt
  0.000000   0.000000   0.000000 (  0.000412)

What I'd like is:

user     system      total        real
sh:touch foo.txt
  0.000000   0.010000   0.030000 (  0.024775)
touch:touch bar.txt
  0.000000   0.000000   0.000000 (  0.000412)

Or something else that only has the results.

I read in another question to use Benchmark.measure but the following also doesn't work:

require 'benchmark'
require 'rake'

n = 3
result = Benchmark.measure do 
  n.times { sh "touch foo.txt" }
end

puts result

result:

touch foo.txt
touch foo.txt
touch foo.txt
  0.000000   0.000000   0.010000 (  0.022931)

How do I benchmark sh and touch but prevent output from going to stdout?

Answer 1

Looking at the source of sh it seems it accepts verbose as an option so the right invocation for you should be:

sh "touch foo.txt", verbose: false

The same can be said of touch:

touch "bar.txt", verbose: false

It seems the docs don't mention these options at all.

Answer 2

You can redirect $stdout

See this example

puts 1
original_stdout = $stdout
$stdout = open("/dev/null", "w")
puts 2
$stdout = original_stdout
puts 3

Which prints

1
3

But does not print 2