素のrandは最悪だとPOSIXが例示してるかなり悪い奴の可能性とかあるので基本的になんであれ避けるべき http://pubs.opengroup.org/onlinepubs/9699919799/functions/rand.html#tag_16_473_06_02
senooken JP Social is a social network, courtesy of senooken. It runs on GNU social, version 2.0.2-beta0, available under the GNU Affero General Public License.
All senooken JP Social content and data are available under the Creative Commons Attribution 3.0 license.