Editing Quine (computing) (section)

==== Source code inspection ====
Quines, per definition, cannot receive ''any'' form of input, including reading a file, which means a quine is considered to be "cheating" if it looks at its own source code. The following [[Unix shell|shell]] script is not a quine:
<syntaxhighlight lang="bash">
#!/bin/sh
# Invalid quine.
# Reading the executed file from disk is cheating.
cat $0
</syntaxhighlight>

A shorter variant, exploiting the behaviour of [[Shebang (Unix)|shebang]] directives:
<syntaxhighlight lang="bash">
#!/bin/cat
</syntaxhighlight>

Other questionable techniques include making use of compiler messages; for example, in the [[GW-BASIC]] environment, entering "Syntax Error" will cause the interpreter to respond with "Syntax Error".

Quine code can also be outputted visually, for example it's used to visualize the neutral zone in [[Yars' Revenge]], along with [[Syntactic_sugar#Syntactic_saccharin|syntactic saccharin]], to obfuscate the source code.