Quine

A “quine” is a self-replicating program — its output is a copy of its own source code.

Here is an example I wrote in Python:

c = """
c = {1}{0}{1}
print(c.format(c, '"'*3))
"""
print(c.format(c, '"'*3))

Shell quine

Shell script quines without "%s"

This shell script prints an exact copy of itself. This means that cat quine.sh and ./quine.sh are equivalent:

quine/quine.sh

Lines 1 to 23 in f1a460d

	#!/bin/sh
	# https://github.com/tingstad/quine
	b='\'
	s=\'
	top='#!/bin/sh
	# https://github.com/tingstad/quine
	'
	src='
	echo "$top
	b=$s$b$s
	s=$b$s
	top=$s$top$s
	src=$s$src$s
	$src"
	'
	echo "$top
	b=$s$b$s
	s=$b$s
	top=$s$top$s
	src=$s$src$s
	$src"

It's therefore also equivalent to running e.g. sh <(sh <(./quine.sh)).

I did not want to use printf %s for this quine. The trick was to get the quoting right on the "recursion line", #14 (which has to match #9), I found the solution here.

In quine2.sh I wanted to avoid variable assignments and minimize string interpretation (no % and $) and just use simple printf and zero-argument functions/procedures.