rails console的readline库问题

rails中可以用使用console命令行来测试运行rails应用程序，但是采用源码编译安装的话可能缺少readline动态库，导致ruby无法使用这个库此时如果调用rails console(rails 3中)会出现以下错误：

/usr/local/lib/ruby/1.9.1/irb/completion.rb:9:in `require': no such file to load -- readline (LoadError)
        from /usr/local/lib/ruby/1.9.1/irb/completion.rb:9:in `'
        from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.0.3/lib/rails/commands/console.rb:3:in `require'
        from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.0.3/lib/rails/commands/console.rb:3:in `'
        from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.0.3/lib/rails/commands.rb:20:in `require'
        from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.0.3/lib/rails/commands.rb:20:in `'
        from script/rails:10:in `require'
        from script/rails:10:in `'

在我的ubuntu 10.4系统中。系统会安装libreadline6这个库，但是缺少libreadline6-dev这个开发库，所以ruby在编译安装的时候无法生成readline这个动态库。此时在ubuntu中用命令：

sudo apt-get install libreadline6-dev或者sudo apt-get install libreadline-dev

这两个命令都会安装libreadline6-dev开发库。安装完后在ruby源码ext/readline目录中，我的是/usr/local/src/ruby-1.9.2-p0/ext/readline下执行：

sudo ruby extconf.rb
sudo make
sudo make install

执行这些命令后，会重新编译安装readline动态库，此时问题便会得到解决。