no such file to load -- zlib uninitialized constant Gem::Commands::InstallCom
#gem install mysql
ERROR: Loading command: install (LoadError)
no such file to load -- zlib
ERROR: While executing gem ... (NameError)


uninitialized constant Gem::Commands::InstallCommand

解决办法是：

进入ruby源码文件夹
安装ruby自身提供的zlib包
#cd ext/zlib
#ruby ./extconf.rb
#make
#make install