cannot load such file -- zlib

When getting started with Ruby, this error might appear:


ERROR: Loading command: install (LoadError)
cannot load such file -- zlib
ERROR: While executing gem ... (NameError)
uninitialized constant Gem::Commands::InstallCommand


However, it is fairly simple to fix. Run the following commands from your terminal.

rvm pkg install zlib
rvm remove 1.9.3
rvm install 1.9.3

Hope that helps!