Ruby function which runs a command and WAITS for it to finish before continuing processing.

runcmd.rb

#!/usr/bin/env ruby

def runcmd(cmd)
  pid  = Process.spawn(cmd)
  Process.wait(pid)
  unless ( $?.exited? && $?.exitstatus == 0 )
    raise "oh noes"
  end
  $?.exitstatus
end

cmd = "sleep 3"
runcmd(cmd)

puts "Hi, world!"