console.txt

ruby test.rb 'puts "42"'
evaluating next: puts "42"
{:result=>nil, :output=>"42\n"}


 ruby test.rb '1+1'      
evaluating next: 1+1
{:result=>2, :output=>""}

test.rb

code = ARGV[0]
puts "evaluating next: #{code}"

require 'stringio'
require 'pp'
new_stdout = StringIO.new
old_stdout = $stdout
$stdout = new_stdout
result = eval code
out = { result: result, output: new_stdout.string}

$stdout = old_stdout
pp out