Quine Program

quine

in computing, a program producing its complete source code as its only output without simply opening the source file of the program and printing the contents (such actions are considered cheating).

This type of program is offered as a somewhat more interesting alternative to HelloWorld programs.

Quines are named after the logician WillardVanOrmanQuine.

---

Why are quines so interesting ? Because they are "obviously impossible".

• Can you print "Hello, world." ?
• Easily.

  print("Hello, world.")

• So now you know how to print *anything*.
• A few things are a bit tricky, but yes -- anything.
• Ah, but can you print quotes around it ?
• It's a bit tricky, but not a problem.

  print("\"Hello, world.\"")

• You've just replaced the problem of the quotes with the problem of the slash.
• No, I can print slashes as well:

  print("quote: \" slash: \\ another slash: \\ another quote: \" The end.")

• Ah, but I bet you can't print the entire program.
• Sure I can.

  print("print(\"Hello, world.\")")

• Yes, that prints the hello world program. But ...
• Oh, I see what you want.

  print("print(\"print(\\\"Hello, world.\\\")\")")

• Yes, that prints *a* program. But it doesn't print *itself*.
• It's a bit awkward, but I suppose you want this:

  print("print(\"print(\\\"print(\\\\\\\"Hello, world.\\\\\\\")\\\")\")")

• Yes, that prints *a* program. But it doesn't print *itself*.

...

• Yes, that prints *a* program. But it doesn't print *itself*.
• Oh. But that would ... that would require an infinite number of escapes.

  print(" <some stuff> <infinite number of slashes >"Hello, world.<infinite number of slashes>" <more stuff> ")

• Sorry, my computer doesn't have an infinite amount of memory.
• Well then. It's impossible for a finite-size source file to hold another copy of the source file inside itself. A thing cannot be bigger than itself.
• Obviously.

---

For starters, here is the classic Quine in SchemeLanguage:

  ((lambda (x) `(,x ',x)) '(lambda (x) `(,x ',x)))

Using outside-language facilities to access the source is considered cheating. E.g. opening the source as a text file would be cheating. But cheating in original ways is strongly encouraged. ;-)

Here is a Quine in ANSI C.

  #include <stdio.h>

  const char *data[] = {
	"  NULL};",
	"",
	"void print_string(const char *str)",
	"{",
	"  const char *ptr;",
	"  printf(\"  \\\"\");",
	"  for (ptr = str; *ptr != 0; ptr++)",
	"	if (*ptr == '\\\\')",
	"	printf(\"\\\\\\\\\");",
	"	else if (*ptr == '\"')",
	"	printf(\"\\\\\\\"\");",
	"	else",
	"	putchar(*ptr); ",
	"  printf(\"\\\",\\n\");",
	"}",
	"",
	"int main(void)",
	"{",
	"  const char **ptr;",
	"  printf(\"#include <stdio.h>\\n\\n\");",
	"  printf(\"const char *data[] = {\\n\");",
	"  for (ptr = data; *ptr != NULL; ptr++)",
	"	print_string(*ptr);",
	"  for (ptr = data; *ptr != NULL; ptr++)",
	"	printf(\"%s\\n\", *ptr);",
	"  return 0;",
	"}",
	NULL};

  void print_string(const char *str)
  {
	const char *ptr;
	printf("  \"");
	for (ptr = str; *ptr != 0; ptr++)
	if (*ptr == '\\')
	printf("\\\\");
	else if (*ptr == '"')
	printf("\\\"");
	else
	putchar(*ptr);
	printf("\",\n");
  }

  int main(void)
  {
	const char **ptr;
	printf("#include <stdio.h>\n\n");
	printf("const char *data[] = {\n");
	for (ptr = data; *ptr != NULL; ptr++)
	print_string(*ptr);
	for (ptr = data; *ptr != NULL; ptr++)
	printf("%s\n", *ptr);
	return 0;
  }

And here's another (much shorter) one invented by AldoCortesi on an idle rainy day:

	int main(void){
	char str[]= "	int main(void){ char str[]= %c%s%c; printf(str, 0x22, str, 0x22);}";
	printf(str, 0x22, str, 0x22);}

Also see: http://www.math.uchicago.edu/~chruska/recursive/selfish.html It contains additional examples.

---

Here's the AldoCortesi quine in C#:

	class Quine { 
	  static void Main() { 
		string f = "class Quine {{{2} static void Main() {{{2}  string f = {0}{1}{0};{2}  System.Console.WriteLine(f, (char)0x22, f, (char)10);{2}  }}{2}}}";
		System.Console.WriteLine(f, (char)0x22, f, (char)10); 
	  }
	}

---

Example in Scheme (and CommonLisp):

  ((lambda (x) (quasiquote ((unquote x) (quote (unquote x))))) (quote (lambda (x) (quasiquote ((unquote x) (quote (unquote x)))))))

which your pretty-printer may let you abbreviate as:

  ((lambda (x) `(,x ', x)) '(lambda (x) `(,x ',x)))

---

A trivial example in Bourne shell:

	#!/bin/sh
	cat $0

but this is really cheating because it is using cat to read its source code. A real SRP contains a copy of its source code within the code itself.

Along the same lines, the one-line script:

	#!/bin/cat

will achieve the same function without running a shell.

For a self-reproducing program in Oberon, see http://www.modulaware.com/mdlt/mdlt78.htm

For a lot more see http://www.nyx.net/~gthompso/quine.htm

---

Here's a PhpLanguage QuineProgram:

  <?
  # PHP Quine written by Ian Kjos - brooke@sf.net
  $y = "function q(\$q) {
	\$q = str_replace('\\\\', '\\\\\\\\', \$q);
	\$q = str_replace('\$', '\\\\\$', \$q);
	\$q = str_replace('\\n', '\\\\n', \$q);
	\$q = str_replace('\"', '\\\\\"', \$q);
	return \$q;
  }

  echo \"<?\\n\\n\";
  echo \"# PHP Quine written by Ian Kjos - brooke@sf.net \\n\\n\";
  echo '\$y = \"' . q(\$y) . '\";';
  echo \"\\n\\neval(\";
  echo '\$y);';
  echo \"\\n\\n\\n\";
  ";
  eval($y);

---

Here's another PHP quine. Is this cheating?? (Also, remove the extra line breaks if you run this, I can't get this wiki to accept single line breaks for some reason) No, it is not cheating. It is actually very good.

  <?php
  // PHP quine by Sam Barnum 360works.com
  // 2003-11-08
  $dna = 'PD9waHAKLy8gUEhQIHF1aW5lIGJ5IFNhbSBCYXJudW0gMzYwd29ya3MuY29tCi8vIDIwMDMtMTEtMDgKJGRuYSA9ICcqJzsKZWNobyBzdHJfcmVwbGFjZShjaHIoNDIpLCAkZG5hLCBiYXNlNjRfZGVjb2RlKCRkbmEpKTsKPz4K';

  echo str_replace(chr(42), $dna, base64_decode($dna));

  ?>

---

And another one in PHP. From my friend [[mailto:yoz@atlas.sk Yoz]]

  <?
  $a='chr(60).chr(63).chr(10).chr(36).chr(97).chr(61).chr(39).$a.chr(39).chr(59).chr(10)."echo $a;".chr(10).chr(63).chr(62)';
  echo chr(60).chr(63).chr(10).chr(36).chr(97).chr(61).chr(39).$a.chr(39).chr(59).chr(10)."echo $a;".chr(10).chr(63).chr(62);
  ?>

---

This php Quine makes it easy to add other actions easily. [[http://basicer.is-a-geek.com Basicer]]

 <?
  function selffunc($a) { print($a . "\n"); print("selffunc(\"" . addcslashes($a,"\n\\\"$") . "\");\n"); }
  selffunc("<?\nfunction selffunc(\$a) { print(\$a . \"\\n\"); print(\"selffunc(\\\"\" . addcslashes(\$a,	\"\\n\\\\\\\"\$\") . \"\\\");\\n\"); }");
  function selfact($a) { print("selfact(\"" . addcslashes($a,"\n\\\"$") . "\");\n"); exec($a); }
  selffunc("function selfact(\$a) { print(\"selfact(\\\"\" . addcslashes(\$a,\"\\n\\\\\\\"\$\") . \"\\\");\\n\");	exec(\$a); }");
  function selffunc2($a) { print("selffunc2(\"" . addcslashes($a,"\\\"$") . "\");\n"); print($a . "\n"); }
  selffunc("function selffunc2(\$a) { print(\"selffunc2(\\\"\" . addcslashes(\$a,\"\\\\\\\"\$\") . \"\\\");\\n\");	print(\$a . \"\\n\"); }");
  //The Self Act Code executes any command.
  selffunc("//The Self Act Code executes any command.");
  selfact("\$a = fopen('log.txt','w'); fwrite(\$a,\"Hello\"); fclose(\$a);");
  selffunc2("?>");
 ?>

---

A short PHP quine is available here: http://www.dionyziz.com/Quine I wish this wiki had a way to add literal characters so that I could directly paste it over, but it won't let me.

---

My short (60 bytes) PHP quine:

<?$a='<?$a=%c%s%c;printf($a,39,$a,39);';printf($a,39,$a,39);

(Actually, the 8 bytes longer "<?php $a='<?php $a=%c%s%c;printf($a,39,$a,39);';printf($a,39,$a,39);" is the preferred form, since the short '<?' may not be supported on all servers)

On the web I found the even shorter PHP quine, written by Trevor Sayre:

<?php printf($a='<?php printf($a=%c%s%c,39,$a,39);',39,$a,39); or <?printf($a='<?printf($a=%c%s%c,39,$a,39);',39,$a,39);

-- Tom van der Beek

---

Here's one in RubyLanguage

  puts(s = <<e, s, 'e')
  puts(s = <<e, s, 'e')
  e

---

And another in RubyLanguage

  s="s=%s;printf s,s.dump";printf s,s.dump

---

Here's one in SuperCollider.

  { thisFunction.asCompileString ++ ".value" }.value

---

In ForthLanguage (assuming that the SuperCollider quine isn't cheating):

 : QUINE   [ SOURCE ] SLITERAL TYPE ; QUINE

But if the quine is allowed to be interpreted code then you can just use this:

 SOURCE TYPE

---

Here's one in JayLanguage

	(,q,q,~]#~[:>:]=q=.'"_)'(,q,q,~]#~[:>:]=q=.'"_)'

aaarg there should be four consecutive single quotes after the first q=. and eight after the second one but I've been unable to convince Wiki to display more than three! Could a Wiki wizard fix this, please?

---

BefungeLanguage

 :0g,:93+`#@_1+

---

In contrast to these concise Zen haiku things pretending to be serious quines, a QuineProgramInCobol wants its own page.

---

Here's one in English language:

  Let the following text, enclosed in double quotes, be called Text A.
  (You can really ignore Text A.  Just take note of the three dollar
  signs it contains.)

  "Let the following text, enclosed in double quotes, be called Text A.
  (You can really ignore Text A.  Just take note of the three dollar signs
  it contains.) $$$ Take pencil and paper, and write the following three
  things down, separated as paragraphs.  (That's just boring copying.
  You needn't be interested in the text you're handling.)  First, all
  of Text A that precedes the three dollar signs.  Second, the whole of
  Text A, enclosed in double quotes.  Third, all of Text A that follows
  the three dollar signs.  Now step back and try to interpret what you
  have just written."

  Take pencil and paper, and write the following three things down,
  separated as paragraphs.  (That's just boring copying.  You needn't
  be interested in the text you're handling.)  First, all of Text A that
  precedes the three dollar signs.  Second, the whole of Text A, enclosed
  in double quotes.  Third, all of Text A that follows the three dollar
  signs.  Now step back and try to interpret what you have just written.

Here is a variant on this idea: Change both "Now step back and try to interpret what you have just written." to "Now follow the instructions that you have just written." to make it into an infinite quine.

---

Some languages provide a bigger challenge than others when it comes to writing quines. Often it is easer to write part of a quine, then write another program that writes the rest. An example is this quine in PathLanguage: http://www.phong.org/bf/quine2.path

If you're masochistic, you may want to write a quine that is also a polyglot (see HelloPolyGlots). Here is a quine that works as CeeLanguage, CeePlusPlus, PerlLanguage and PythonLanguage:

 #include <stdio.h>
 #define q(a,...) a
 #define substr q
 #define eval(a) main(){char c[]=a,n=10;c[419]=0;printf(c+4,n,n,n,n,34,34,n,34,39,c+4,39,34,n); }/* Copyright (C) Thomas Schumm <phong@phong.org>
 exec("from sys import*;substr=q=lambda y:exit(stdout.write(y[4:-46]%((10,)*4+(34,34,10,34,39, y[4:-46],39,34,10))))",None);#*/
 eval(substr(q("$p='#include <stdio.h>%c#define q(a,...) a%c#define substr q%c#define eval(a) main() {char c[]=a,n=10;c[419]=0;printf(c+4,n,n,n,n,34,34,n,34,39,c+4,39,34,n); }/* Copyright (C) Thomas Schumm <phong@phong.org>%cexec(%cfrom sys import*;substr=q=lambda y: exit(stdout.write(y[4:-46]%%((10,)*4+(34,34,10,34,39,y[4:-46],39,34,10))))%c,None);# */%ceval(substr(q(%c$p=%c%s%c;printf($p,(10)x4,34,34,10,34,39,$p,39,34,10)%c),1,-1))%c'; printf($p,(10)x4,34,34,10,34,39,$p,39,34,10)"),1,-1))

When I compiled and ran as C/C++, it didn't work (missing only a few characters)--a change made to gcc?

Working fine for me with gcc 3.3.4...

The original is here (I may occasionally update it if it gets better or smaller): http://www.phong.org/bf/polyglotC++PerlPythonC.c

-- TomSchumm

---

Here is a quine in MS-DOS (that I made up myself):

 @echo off
 %1 %2
 call %0 goto e %%
 call %0 goto e %%3 echo.%%4
 echo :f
 goto f
 :e
 echo.%4@echo off
 echo.%4%31 %32
 echo.%4call %30 goto e %3%3
 echo.%4call %30 goto e %3%33 echo.%3%34
 echo.%4echo :f
 echo.%4goto f
 echo.%4:e
 :f

---

I made a correct QBASIC quine:

 A$ = "a!'dbde[39] c34);[97] 'a + c34);[98] 'b';[99] 'c';[100][101] 'e';[91] : PRINT 'CASE c';[93] ']';[33] A$;dCASE ELSE: PRINT MID$(A$, I, 1);dEND SELECTdNEXT Id"
 FOR I = 1 TO LEN(A$)
 SELECT CASE MID$(A$, I, 1)
 CASE CHR$(39): PRINT CHR$(34);
 CASE CHR$(97): PRINT "A$ = " + CHR$(34);
 CASE CHR$(98): PRINT "FOR I = 1 TO LEN(A$)";
 CASE CHR$(99): PRINT "CHR$(";
 CASE CHR$(100): PRINT
 CASE CHR$(101): PRINT "SELECT CASE MID$(A$, I, 1)";
 CASE CHR$(91): PRINT : PRINT "CASE CHR$(";
 CASE CHR$(93): PRINT "): PRINT";
 CASE CHR$(33): PRINT A$;
 CASE ELSE: PRINT MID$(A$, I, 1);
 END SELECT
 NEXT I

---

Possibly the shortest quine of all can be written in the (original, pre-Visual) BASIC language. It reproduces itself whether you list it or run it. Here it is:

1. LIST

But this (and any other program) that simply outputs a source code listing should be considered cheating - for a quine to be a true quine, it must surely involve quotation.

[Yes, this is cheating. The canonical shortest quine using this sort of cheat was in c, with a compiler that would accept an empty file as input and construct an executable that echoed nothing to stdout. I can't recall if this was standard-conforming or just undefined behaviour though...]

Almost all scripting languages allow the 'empty program' cheat. [Yeah, but it is less interesting with an interpreter - and this instance predates most scripting languages.]

[It is questionable whether the 'empty program' approach even counts as cheating. It is cheating for a quine to access its own source code, either via file i/o or via special language functionality like "LIST", but an empty program does no such thing.]

---

Years ago I came across a programming challenge (in a magazine I believe) that asked the competitors to write a QuineProgram. When the answers were published, the one that I thought was particularly clever went as follows:

• Start with any compiler.
• Write a program that will not compile.
• Take the error report from the compiler and compile it. This will most likely not compile.
• Take the new error report and compile it. Repeat until the output matches the input.
• If you consider the compiler as an interpreter (rather than a compiler) you now have a program that produces its source code as it's ouput when interpreted by the compiler.

-- ChrisHines

I tried this approach with GCC. However, I always end up with a cycle of length 2. Moreover, since GCC reports file names in its error messages, the name of the file is significant (how unelegant).

-- StephanHouben

quine.c:1: parse error before '.' token

This works for me with mingw.

 Borland C++ 5.5.1 for Win32 Copyright (c) 1993, 2000 Borland
 bcc32_interpreter_quine.c:
 Error E2141 bcc32_interpreter_quine.c 1: Declaration syntax error
 Error E2223 bcc32_interpreter_quine.c 1: Too many decimal points
 *** 2 errors in Compile ***

this works for me in SuperCollider:

� ERROR: Parse error

	in file 'selected text'
	line 1 char 10 :
	ERROR:� Parse error
	in file 'selected text'
 -----------------------------------
 � ERROR: Command line parse failed
 nil

all parse errors seem to converge to this fixed point.

---

A basic AqABqB-style quine in NemerleLanguage:

 using System.Console;
 module quine {
	Main():void {
	 def a = @"using System.Console;
 module quine {
	Main():void {
	 def a = @;
	 Write(a.Substring(0,72));Write(34:>char);
	 Write(a);Write(34:>char);
	 Write(a.Substring(72,(a.Length -72)));
	}
 }
 ";
	 Write(a.Substring(0,72));Write(34:>char);
	 Write(a);Write(34:>char);
	 Write(a.Substring(72,(a.Length -72)));
	}
 }

---

Excel

=SUBSTITUTE(SUBSTITUTE("=SUBSTITUTE(SUBSTITUTE(#@#,CHAR(35),CHAR(34)),CHAR(64),#@#)",CHAR(35),CHAR(34)),CHAR(64),"=SUBSTITUTE(SUBSTITUTE(#@#,CHAR(35),CHAR(34)),CHAR(64),#@#)")

--Jonathan Rynd

 =SUBSTITUTE("=SUBSTITUTE(@,CHAR(64),CHAR(34)&@&CHAR(34))",CHAR(64),CHAR(34)&"=SUBSTITUTE(@,CHAR(64),CHAR(34)&@&CHAR(34))"&CHAR(34))

--dave@burt.id.au

---

PostScript:

 (dup == =)
 dup == =

(note this doesn't produce output to paper, but rather to the terminal; run it with gs)

--Chris King

---

RexxLanguage has a SOURCELINE command that prints the source of a line of the program (meant for use with error messages), so the following should work as a Quine in REXX (don't have an interpreter to check right now):

 sourceline 1

That's cheating, though, akin to the bash one above that uses cat $0

---

 ;; (*.) = {- *) let (@@) x y = x::y let e = [] let a = (*
 (letrec ((a '(
 ; -} -- *)
  "								" @@
  "			A polyglot quine in			" @@
  "			Haskell & O'Caml & Scheme			" @@
  "								" @@
  "  Usage:  runhugs thisfile		# www.haskell.org/hugs  " @@
  "	  ocamlc -o x thisfile.ml ;./x  # www.ocaml.org	 " @@
  "	  scsh -s thisfile		# www.scsh.net	  " @@
  "								" @@
  "" @@
  ";; (*.) = {- *) let (@@) x y = x::y let e = [] let a = (*" @@
  "(letrec ((a '(" @@
  "; -} -- *)" @@
  "" @@
  " e" @@
  ";; (*:) = [\" \" ++ show x ++ \" @@\" | x<-( *.)]; main = {-" @@
  "; -} mapM_ putStrLn (x ++ ( *:) ++ y); (x, _:y) = {-" @@
  "; -} span p (tail (dropWhile p ( *.))); p = (/= \"\"); infixr {-" @@
  "; -} @@; (@@) = (:); e = [] {- *) let rec s = function [] -> (*" @@
  "; *) [],[] | x::y -> if x = \"\" then [],y else let a,b = s y (*" @@
  "; *) in x::a,b let b,d = s (snd (s a)) let f = String.escaped (*" @@
  "; *) let c = List.map (fun x -> \" \\\"\" ^ f x ^ \"\\\" @@\") a" @@
  ";; List.iter (fun x -> print_endline x) (b @ c @ d) (*" @@
  ")) (f (lambda (x) (if (null? x) x (if (string? (car x)) (cons (" @@
  "car x) (f (cdr x))) (f (cdr x)))))) (g (lambda (x) (if (string=?" @@
  "\"\" (car x)) (cons '() (cdr x)) (let ((y (g (cdr x)))) (cons (" @@
  "cons (car x) (car y)) (cdr y)))))) (h (lambda (x) (if (null? x)" @@
  "#f (begin (display (car x)) (newline) (h (cdr x)))))) (i (lambda" @@
  "(x) (if (null? x) #f (begin (display \" \") (write (car x)) (" @@
  "display \" @@\") (newline) (i (cdr x))))))) (let ((b (g (cdr (g" @@
  "(f a)))))) (h (car b)) (i (f a)) (h (cdr b))))" @@
  "; -} -- *)" @@
  e
 ;; (*:) = [" " ++ show x ++ " @@" | x<-( *.)]; main = {-
 ; -} mapM_ putStrLn (x ++ ( *:) ++ y); (x, _:y) = {-
 ; -} span p (tail (dropWhile p ( *.))); p = (/= ""); infixr {-
 ; -} @@; (@@) = (:); e = [] {- *) let rec s = function [] -> (*
 ; *) [],[] | x::y -> if x = "" then [],y else let a,b = s y (*
 ; *) in x::a,b let b,d = s (snd (s a)) let f = String.escaped (*
 ; *) let c = List.map (fun x -> " \"" ^ f x ^ "\" @@") a
 ;; List.iter (fun x -> print_endline x) (b @ c @ d) (*
 )) (f (lambda (x) (if (null? x) x (if (string? (car x)) (cons (
 car x) (f (cdr x))) (f (cdr x)))))) (g (lambda (x) (if (string=?
 "" (car x)) (cons '() (cdr x)) (let ((y (g (cdr x)))) (cons (
 cons (car x) (car y)) (cdr y)))))) (h (lambda (x) (if (null? x)
 #f (begin (display (car x)) (newline) (h (cdr x)))))) (i (lambda
 (x) (if (null? x) #f (begin (display " ") (write (car x)) (
 display " @@") (newline) (i (cdr x))))))) (let ((b (g (cdr (g
 (f a)))))) (h (car b)) (i (f a)) (h (cdr b))))
 ; -} -- *)

D'oh, that's got me beat. -- TomSchumm

---

What about my bash quine?

 b=\' c=\\ a='echo b=$c$b c=$c$c a=$b$a$b; echo $a'
 echo b=$c$b c=$c$c a=$b$a$b; echo $a

-- Tafuni Vito - Italy - vitotafuni_AT_gmail.com

Great.

Here's a shell quine based on that one, but on one line:

 b=\' c=\\ a='echo -n b=$c$b c=$c$c a=$b$a$b\;; echo $a';echo -n b=$c$b c=$c$c a=$b$a$b\;; echo $a

---

 repeat x 2 : output xpose list 2 crlf <<"
 repeat x 2 : output xpose list 2 crlf <<"

---

In ExtendedObjectTcl

 Object ::quine
 ::quine proc printSelf {  } {
 foreach instance [ Object info instances ] {
 foreach proc [ $instance info procs ] {
 puts "Object $instance"
 puts "$instance proc $proc \{ [ $instance info args $proc ] \} \{
 [ $instance info body $proc ]
 \}"
 }
 }
 puts "::quine printSelf"
 }
 ::quine printSelf

Does introspection count as cheating?

---

How could we forget HQ9+ (HqNinePlusLanguage)?

 q

---

Java Quine:

  public class Quine {
	public static void main(String[] args) {
	String[] str = {
  "public class Quine {",
  " public static void main(String[] args) {",
  "  String[] str = {",
  "  };",
  "  for(int i=0;i<3;i++)System.out.println(str[i]);",
  "  for(int i=0;i<9;i++)System.out.println((char)34+str[i]+(char)34+',');",
  "  for(int i=3;i<9;i++)System.out.println(str[i]);",
  " }",
  "}",
	};
	for(int i=0;i<3;i++)System.out.println(str[i]);
	for(int i=0;i<9;i++)System.out.println((char)34+str[i]+(char)34+',');
	for(int i=3;i<9;i++)System.out.println(str[i]);
	}
  }

--JasonWilson?

Sorry, just had to:

  enum Q{T;System a;String b="enum Q{T;System a;String b=%c%s%c;{a.out.printf(b,34,b,34);a.exit(0);}}";{a.out.printf(b,34,b,34);a.exit(0);}}

--lf

---

Pascal/Delphi:

const a=';begin write(^#^/^.^3^4^`^!^}#39,a,#39,a)end.';begin write(^#^/^.^3^4^`^!^}#39,a,#39,a)end.

--Geoffrey Swift (http://www.trollied.org/~blimey/quines.php)

---

OK I've got to ask: would it be cheating for the program to access its binary image, reverse compile itself, and write the result to stdout?

---

Seew SelfReplication, MixingLevels, SelfAssembly

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Yet another php quine, by vejux. Php specific. It processes its own output, not the source code, so it should not be concidered cheating. (Use single new lines)

<?

function c($b) { return "<"."?\n$b?".">\n$b"; } ob_start("c");

?>

function c($b) { return "<"."?\n$b?".">\n$b"; } ob_start("c");

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A (cheaty) PHP quine:

<?=file_get_contents(__FILE__)?>

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I took Tafuni Vito's BASH quine above and made a fork bomb with it:

	b=\' c=\\ a='yes $( echo b=$c$b c=$c$c a=$b$a$b; echo $a ) | bash &'
	yes $( echo b=$c$b c=$c$c a=$b$a$b; echo $a ) | bash &

It's a lot more heavy-duty than a traditional fork bomb, so don't complain to me if it made your system crash.

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The following is (probably) the shortest possible Quine in PL/I. It only compiles with he old V2.3.0 compiler and requires a few non-standard compiler options, COMPILE and MAR(1,90,0) (Source starts in column 1!)

%dcl z%z=&apos;put edit&apos;;proc options(main;q=&apos;&apos;&apos;&apos;put list(m;do i=1,2;z(q)skip;do j= 1to 78c=substr(m(i),j;if c=q z(c;z(c;end;z(q&apos;,&apos;;dcl(c,q)char,m(2)char(99)init( &apos;%dcl z%z=&apos;&apos;put edit&apos;&apos;;proc options(main;q=&apos;&apos;&apos;&apos;&apos;&apos;&apos;&apos;put list(m;do i=1,2;z(q)skip;do j=&apos;, &apos;1to 78c=substr(m(i),j;if c=q z(c;z(c;end;z(q&apos;&apos;,&apos;&apos;;dcl(c,q)char,m(2)char(99)init(&apos;,

This entry has big trouble with repeated single quotes...

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"Hello" is a quine in many languages?

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An old IOCCC entry forever cinched the spot of shortest quine - at one point, gcc would, given the right compiler switches, compile a zero-byte C program into a program that does nothing. Thus, it is a zero-byte program that produces a zero-byte output - a perfect quine!