no such file to load -- zlib

或者提示
fatal error： zlib.h： No such file or directory
都是一个意思，又忘了是哪个包了，所以再记一次。

zlib缺失
:~$ sudo gem install rails
ERROR:  Loading command: install (LoadError)
    no such file to load -- zlib
ERROR:  While executing gem ... (NameError)
    uninitialized constant Gem::Commands::InstallCommand
解决：
下载zlib
sudo apt-get install zlib1g-dev
到ruby源代码：
#:~/software/ruby-1.9.2-p180/ext/zlib$ ruby extconf.rb