Have a ruby script output what version of ruby is running it

How do I have my ruby script output what version of r开发者_如何学编程uby is running it?

The RUBY_VERSION constant contains the version number of the ruby interpreter and RUBY_PATCHLEVEL contains the patchlevel, so this:

puts RUBY_VERSION

outputs e.g. 2.2.3, while this:

puts RUBY_PATCHLEVEL

outputs e.g. 173. Together it can be used like this:

ruby -e 'print "ruby #{ RUBY_VERSION }p#{ RUBY_PATCHLEVEL }"'

to output e.g. ruby 2.2.3p173

For reference, here's how variables and constants work, along with a list of Ruby's built-in variables and constants: Ruby Programming/Syntax/Variables and Constants and Pre-defined Variables.

You can get a list of all the global constants here, including RUBY_VERSION and friends, in the official Ruby language documentation.

For the bonus round, this will tell you some more useful info about your Ruby environment using RbConfig:

require 'rbconfig'
puts Config::CONFIG.sort_by{ |n,v| n.downcase }.map{ |n,v| "#{n} => '#{v}'" }