Print prettified JSON from file or STDIN. Save this file as `~/bin/json`.

prettyJson.js

#!/usr/bin/env node

var filename = process.argv[2];
if (filename) {
  var json = require('fs').readFileSync(filename).toString('utf-8');
  printPretty(json);
} else {
  var json = '';
  process.stdin.setEncoding('utf-8');
  process.stdin.on('data', function (chunk) {
    json += chunk;
  });
  process.stdin.on('end', function () {
    printPretty(json);
  });
}

function printPretty(json) {
  var pretty = JSON.stringify(JSON.parse(json), null, 2);
  console.log(pretty);
}