JSON

The python standard library provides a json library that can be used to pretty print json.

$  echo '{"this": ["that"]}' | python -m json.tool
{
  "this": [
      "that"
  ]
}

XML

$  echo '<root><foo a="b">lorem</foo><bar value="ipsum" /></root>' | xmllint --format -
<?xml version="1.0"?>
<root>
  <foo a="b">lorem</foo>
  <bar value="ipsum"/>
</root>

Install on ubuntu:

sudo apt-get install libxml2-utils

recommendation from: http://stackoverflow.com/questions/16090869/how-to-pretty-print-xml-from-the-command-line