Mac のruby のirb で日本語入力をできるようにする - Slow Dance
http://d.hatena.ne.jp/LukeSilvia/20080802/p1
Ruby 1.8.7 を ports で入れると、GNU Readlineという入力系のライブラリが更新して、問題が解消するとのこと。
（あ、Readlineだけ更新して様子をみてみればよかったです。）
$ sudo port install ruby +darwin_9 +mactk
Password: ---> Fetching readline ---> Attempting to fetch readline52-001 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-002 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-003 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-004 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-005 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-006 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-007 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-008 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-009 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-010 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-011 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline52-012 from http://ftp.gnu.org/gnu/readline/readline-5.2-patches/ ---> Attempting to fetch readline-5.2.tar.gz from http://ftp.gnu.org/gnu/readline ---> Verifying checksum(s) for readline ---> Extracting readline ---> Applying patches to readline ---> Configuring readline ---> Building readline with target all ---> Staging readline into destroot ---> Installing readline 5.2.012_1 ---> Activating readline 5.2.012_1 ---> Cleaning readline ---> Fetching ruby ---> Attempting to fetch ruby-1.8.7-p72.tar.bz2 from http://www.ibiblio.org/pub/languages/ruby/1.8 ---> Verifying checksum(s) for ruby ---> Extracting ruby ---> Applying patches to ruby ---> Configuring ruby ---> Building ruby with target all ---> Staging ruby into destroot ---> Installing ruby 1.8.7-p72_2+thread_hooks ---> Activating ruby 1.8.7-p72_2+thread_hooks ---> Cleaning ruby
日本語でました。
bash-3.2$ ruby -v ruby 1.8.7 (2008-08-11 patchlevel 72) [i686-darwin9] bash-3.2$ irb irb(main):001:0> puts '日本語こんにちは' 日本語こんにちは => nil irb(main):002:0>
