Read JSON from standard input and writes formatted JSON to standard output. Requires Node.js.

formatjson.js

#!/usr/bin/env node

// Reads JSON from stdin and writes equivalent
// nicely-formatted JSON to stdout.

var input = '';

process.stdin.resume();
process.stdin.setEncoding('utf8');

process.stdin.on('data', function (chunk) {
    input += chunk;
});

process.stdin.on('end', function () {
    var parsedData = JSON.parse(input);
    var outputJSON = JSON.stringify(parsedData, null, '    ');
    process.stdout.write(outputJSON);
});