require 'open4'
#
# when using block form the child process is automatically waited using
# waitpid2
#

status =
  Open4::popen4("sh") do |pid, stdin, stdout, stderr|
    stdin.puts "echo 42.out"
    stdin.puts "echo 42.err 1>&2"
    stdin.close

    puts "pid        : #{ pid }"
    puts "stdout     : #{ stdout.read.strip }"
    puts "stderr     : #{ stderr.read.strip }"
  end

    puts "status     : #{ status.inspect }"
    puts "exitstatus : #{ status.exitstatus }"