module Commander::UI

def enable_paging
  return unless $stdout.tty?
  return unless Process.respond_to? :fork
  read, write = IO.pipe
  # Kernel.fork is not supported on all platforms and configurations.
  # As of Ruby 1.9, `Process.respond_to? :fork` should return false on
  # configurations that don't support it, but versions before 1.9 don't
  # seem to do this reliably and instead raise a NotImplementedError
  # (which is rescued below).
  if Kernel.fork
    $stdin.reopen read
    write.close
    read.close
    Kernel.select [$stdin]
    ENV['LESS'] = 'FSRX' unless ENV.key? 'LESS'
    pager = ENV['PAGER'] || 'less'
    exec pager rescue exec '/bin/sh', '-c', pager
  else
    # subprocess
    $stdout.reopen write
    $stderr.reopen write if $stderr.tty?
    write.close
    read.close
  end
rescue NotImplementedError
ensure
  write.close if write && !write.closed?
  read.close if read && !read.closed?
end