`require': no such file to load -- readline (LoadError)

Compiling Ruby from source may cause this error to fire when trying to script/console:

`require': no such file to load -- readline (LoadError)

This snippet tells you the simple commands to fix it. Unfortunately, on my Ubuntu installation, the libreadline5-dev package was not installed, so "ruby extconf.rb" failed. After installing libreadline5-dev according to this article, the snippet then worked.