code: function (seed, cb) {
          exec('uname -a', function (err, uname) {
              var userAgent = {};
              for (var field in seed) {
                  userAgent[field] = encodeURIComponent(seed[field]);
              }
  
              // URI-encode in case there are unusual characters in the system's uname.
              userAgent.uname = encodeURIComponent(uname) || 'UNKNOWN';
  
              cb(JSON.stringify(userAgent));
          });
      }
docs: Gets a JSON version of a User-Agent by encoding a seeded object and fetching a uname from the system.