Reads JSON from stdin; pretty prints it to stdout.

ppjson.js

#!/usr/bin/env node

var flatJSON = '';

process.stdin.on('data', function(data) {
  flatJSON = flatJSON + data;
});
process.stdin.on('end', function() {
  prettyJSON = JSON.stringify( JSON.parse(flatJSON), null, 2 )
  console.log(prettyJSON);
});

process.stdin.resume();

Don't forget to chmod +x ppjson.js