升级ruby和rails后进入script/consle出现：
/usr/local/lib/ruby/1.8/irb/completion.rb:10:in `require': no such file to load -- readline (LoadError)
from /usr/local/lib/ruby/1.8/irb/completion.rb:10
from /usr/local/lib/ruby/1.8/irb/init.rb:252:in `require'
from /usr/local/lib/ruby/1.8/irb/init.rb:252:in `load_modules'
from /usr/local/lib/ruby/1.8/irb/init.rb:250:in `each'
from /usr/local/lib/ruby/1.8/irb/init.rb:250:in `load_modules'
from /usr/local/lib/ruby/1.8/irb/init.rb:21:in `setup'
from /usr/local/lib/ruby/1.8/irb.rb:54:in `start'
from /usr/local/bin/irb:13
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解决办法：
第一步：确认是否安装了libncurses5-dev libreadline5-dev ,如果没有安装，就用
sudo apt-get install libncurses5-dev libreadline5-dev 进行安装
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第二步：
cd /usr/src/ruby-1.8.7/ext/readline
ruby extconf.rb
make
sudo make install
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