$ ruby -v
ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-linux]
$ gem -v
2.4.8
$ asciidoctor -v
Asciidoctor 1.5.3 [http://asciidoctor.org]
Runtime Environment (ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-linux]) (lc:UTF-8 fs:UTF-8 in:- ex:UTF-8)
$ uname -a
Linux veg 4.1.12-gentoo #1 SMP PREEMPT Fri Nov 6 18:19:36 JST 2015 x86_64 Intel(R) Core(TM) i7-4500U CPU @ 1.80GHz GenuineIntel GNU/Linux
(veg is a hostname.)