This was started as an exercise. I wanted to create a quine from scratch with running elk inrton:

      ^^..^^           ^^..^^ 
   _____ U         _____ U    
 ~(  _  /    =>  `(  _  /     
   || ||           // \\      
   ^^ ^^          ^^   ^^     

Saved evolution to see how I was figuring stuff out. I had no previous experience in creating quines. Showing the evolution of my thought, history goes:

quine.alpha.rb => quine.beta.rb => quine.rb

It is very interesting to observe how figuring stuff out happened. You can run and observe running elk with:

ruby runner.rb

There is an animated version of this quine. If you run it with no args (or through a runner) it is just a regular quine. But if you provide number of frames and pause in seconds between frames, the elk will go right and return back the specified number of frames:

ruby quine.anim.rb 30 0.2

No specific obfuscation was made to the code. I also tried to keep line length below 100.

Based on the same technic the quine derivative sha.quine.* outputs it's own sha checksum using provided algorithm. Defaults to sha1. To examine:

ruby sha.quine.rb
sha1sum sha.quine.rb

ruby sha.quine.rb sha512
sha512sum sha.quine.rb

node sha.quine.js sha224
sha224sum sha.quine.js

node sha.quine.py sha256
sha256sum sha.quine.py

# ... etc

With ruby it is sufficient to write just one half and it will work like a generator. Running:

ruby palindrome-quine-generator.rb

and

ruby palindrome-quine.rb

yields the same output which is palindrome-quine.rb contents.

Reverting it:

File.write('palindrome-quine-reversed.rb', File.read('palindrome-quine.rb').chars.reverse.join)

Creates the file identical to the palindrome-quine.rb.

As I was discovering new interesting new possibilities I went further. Greatly inspired by Yusuke Endoh I have created an animated ASCII-art quine

ruby quine.ascii.anim.rb

You can see that it can generate itself from a draft non-ascii version.