Yosemite から El Capitan にアップデートしたら、rails sをしたら、
bin/rails:6: warning: already initialized constant APP_PATH
***/bin/rails:6: warning: previous
definition of APP_PATH was here Usage: rails COMMAND [ARGS]
The most common rails commands are: generate Generate new code
(short-cut alias: "g") console Start the Rails console (short-cut
alias: "c") server Start the Rails server (short-cut alias: "s")
dbconsole Start a console for the database specified in
config/database.yml
(short-cut alias: "db") new Create a new Rails application. "rails new my_app" creates a
new application called MyApp in "./my_app"
In addition to those, there are: application Generate the Rails
application code destroy Undo code generated with "generate"
(short-cut alias: "d") plugin new Generates skeleton for developing
a Rails plugin runner Run a piece of code in the application
environment (short-cut alias: "r")
All commands can be run with -h (or --help) for more information.
と出るようになってしまいました。
rake rails:update:bin を打つと、情報が出てくるということで（http://ja.stackoverflow.com/questions/10290/warning-already-initialized-constant-app-path）打ってみたところ、
Library not loaded: libmysqlclient.18.dylib (LoadError) と出てしまいました。。。
どうやら、 libmysqlclient.18.dylib が見つからない模様。
Yosemite までは、 sudo ln -s /usr/local/mysql/lib/libmysqlclient.18.dylib /usr/lib/libmysqlclient.18.dylib とやるといいらしいんですが、例によってできないので、
sudo ln -s /usr/local/mysql/lib/libmysqlclient.18.dylib /usr/local/lib/libmysqlclient.18.dylib
El Capitanだとこれが有効なようです。
これで、Library not loaded: libmysqlclient.18.dylib (LoadError) は出なくなりました。