Selfish Code

The following collection of self-reproducing code in various programming languages was collected by Joe Miller and myself. We started from some standard examples in C and tried to generalize to other languages.

Near the bottom, you can find code that is simultaneously selfish in more than one language! So far Joe has dual selfish C-tcl and C-lisp code. Anyone care to give it a try? Particularly challenging would be, say, Fortran-TeX or, even worse, three languages.

I haven't updated this page in a long time. For a much larger collection of selfish code, you should check out Gary Thompson's Quine Page, which contains many of the programs listed here, among others.

The following is a collection of ``selfish'' programs. Selfish programs are self-reproducing programs; programs that produce their own source code. Because of the diversity of languages I don't have a strict definition of selfish. In a functional language a selfish program usually evaluates to itself. In an imperative language a selfish program usually prints itself out. There is no reason to make these hard and fast rules though. I included anything that was short, clever, or interesting. There are a huge number of languages and almost all of them admit selfish programs. This is by no means a canonical list, but perhaps someday it will be.

Language: C

main(){char *c="main(){char *c=%c%s%c;printf(c,34,c,34);}";printf(c,3
4,c,34);}

p="p=%c%s%c;main(){printf(p,34,p,34);}";main(){printf(p,34,p,34);}

#include<stdio.h>
main(){char*c="\\\"#include<stdio.h>%cmain(){char*c=%c%c%c%.102s%cn%c
;printf(c+2,c[102],c[1],*c,*c,c,*c,c[1]);exit(0);}\n";printf(c+2,c[10
2],c[1],*c,*c,c,*c,c[1]);exit(0);}

#define T(a) main(){printf(a,#a);}
T("#define T(a) main(){printf(a,#a);}\nT(%s)")

/**/char q='"',*a="*//**/char q='%c',*a=%c%s%c*/};)b(stup;]d[b=]d-852
[b)--d(elihw;)q,a,q,q,2+a,b(ftnirps{)(niam;031=d tni;]952[b,",b[259];
int d=130;main(){sprintf(b,a+2,q,q,a,q);while(d--)b[258-d]=b[d];puts(
b);}/*c%s%c%=a*,'c%'=q rahc/**//*"=a*,'"'=q rahc/**/

Pretty short, eh?

Language: Java

import java.text.*;class a{public static void main(String x[]){char b[]={34};
char c[]={123};String s[]=new String[3];s[0]="import java.text.*;class a{2}
public static void main(String x[]){2}char b[]={2}34};char c[]={2}123};
String s[]=new String[3];s[0]={1}{0}{1};s[1]=new String(b);s[2]=new String(c);
System.out.println(MessageFormat.format(s[0],s));}}";s[1]=new String(b);s[2]=
new String(c);System.out.println(MessageFormat.format(s[0],s));}}

Language: Pascal

{ One single line }
CONST T=';BEGIN WRITE(#67#79#78#83#84#32#84
#61#39,T,#39,T)END.';BEGIN WRITE(#67#79#78#83
#84#32#84#61#39,T,#39,T)END.

CONST A=';VAR S,T:STRING;BEGIN READLN(S);READLN(T); WRITELN(S+T=#67#79#78#83#84#32#65#61#39+A+#39+A)END.'
;VAR S,T:STRING;BEGIN READLN(S);READLN(T);WRITELN(S+T=#67#79#78#83#84#32#65#61#39+A+#39+A)END.

Language: Tcl

set x {set x {@}; regsub @ $x $x x; set x}; regsub @ $x $x x; set x

join [split a{a} a] {join [split a{a} a] }

join {{} \{ \}} {join {{} \{ \}} }

Language: LISP

T

((LAMBDA (X) (LIST X (LIST 'QUOTE X))) '(LAMBDA (X) (LIST X (LIST 'QU
OTE X))))

((LAMBDA (X) `(,X ',X)) '(LAMBDA (X) `(,X ',X)))

Language: Fortran 77

      character*999s,p 
       datas/'''/end(6x,a17/3(5x,a1,a66/),6x,a40/6x,a66/6x,a3)character*
     '999s,p datas/p=s(64:70)//s(:1)//s(:1)//s(:176)//s(:2)write(*,s(6:5
     '6))s(48:),p,p,s,p(67:),s,p(133:),s(71:),s(111:),s(3:)'/           
      p=s(64:70)//s(:1)//s(:1)//s(:176)//s(:2)
      write(*,s(6:56))s(48:),p,p,s,p(67:),s,p(133:),s(71:),s(111:),s(3:)
      end

Language: BASIC

10 LIST

10 LIST : REM MER : TSIL 01

a$=chr$(34):d$=chr$(58)+chr$(99)+chr$(36)+chr$(61):b$="a$=chr$(34):d$
=chr$(58)+chr$(99)+chr$(36)+chr$(61):b$=":c$=":?b$ a$ b$ a$ d$ a$ c$ 
a$ c$":?b$ a$ b$ a$ d$ a$ c$ a$ c$

a$[1]="a$[":a$[2]="]=":a$[3]="q$=chr$(34):for i=1 to 3:?a$[1]str$(i)a
$[2]q$ a$[i]q$ chr$(58);:next i:?a$[3]":q$=chr$(34):for i=1 to 3:?a$[
1]str$(i)a$[2]q$ a$[i]q$ chr$(58);:next i:?a$[3]

a$="?chr$(97)chr$(36)chr$(61)chr$(34)a$ chr$(34)chr$(58)a$":?chr$(97)
chr$(36)chr$(61)chr$(34)a$ chr$(34)chr$(58)a$

Language: AWK

BEGIN{c="BEGIN{c=%c%s%c;printf(c,34,c,34);}";printf(c,34,c,34);}

Language: MUMPS (now called just M)

S Y=$C(34),A="W ""S Y=$C(34),A=""_Y X ""F %=1:1:6 W $P(A,Y,%),Y,Y"" W
Y,"" X A""" X A

Language: Perl

#!/usr/bin/perl

seek DATA, 0, 0;
print ;

__DATA__

$b='$b=%c%s%c;printf$b,39,$b,39;';printf$b,39,$b,39;

Language: TeX

 \documentclass{book}\pagestyle
{empty}\def\a{\ensuremath{\backslash}}\def\f
{\def\b{\a}\def\c{\{}\def\d{\}}\def
\e{\\}\noindent\g\b def\b g\c\def\b{\a b
}\def\c{\a c }\def\d{\a d}\def\e{\a e
\\}\g\}\a begin\{document\}\a f\a end
\{document\}}\def\g{ \b documentclass\c book\d\b pagestyle\e
\c empty\d\b def\b a\c \b ensuremath\c \b backslash\d\d\b def\b f\e
\c \b def\b b\c \b a\d\b def\b c\c \b \c \d\b def\b d\c \b \d\d\b def\e
\b e\c \b \b \d\b noindent\b g\b b def\b b g\b c\b def\b b\c \b a b\e
\d\b def\b c\c \b a c \d\b def\b d\c \b a d\d\b def\b e\c \b a e\e
\b \b \d\b g\b \d\b a begin\b \c document\b \d\b a f\b a end\e
\b \c document\b \d\d}\begin{document}\f\end{document}

\obeylines\nopagenumbers\tt\def\[#1]#2[#3[#4
#5{#1obeylines#1nopagenumbers#1tt#1def#1[#21]#22[#23[#24
#25#3#5#4#1[#1char92]#1#2[#1char123[#1char125
#3#1[#1#21]#1#22[#1#23[#1#24
#3#1#25#4#4#1bye}\[\char92]\#[\char123[\char125
{\[\#1]\#2[\#3[\#4
{\#5}}\bye

Multiple Languages:

Author: Joe Miller
Languages: C and tcl

#define set char*f=
#define F
#define proc main(){
set F "#define set char*f=
#define F
#define proc main(){
set F %c%s%c;
proc /* {} {}
puts -nonewline %cformat %cF 34 %cF 34 91 36 36]
set a {*/printf(f,34,f,34,91,36,36);}
";
proc /* {} {}
puts -nonewline [format $F 34 $F 34 91 36 36]
set a {*/printf(f,34,f,34,91,36,36);}

t(setq /*;*/){}main(){char q='\"',s='\\';char*a=
"~%t(setq /*;*/){}main(){char q='~A';char*a=
~S;char*b=/*
)(setq a ~S)
(setq */ ~S;printf(b,s,q,s,s,q,a,q,q,s,s,s,q,s,s,s,s,q,q,b,q/*
)(format t /* a /* a */);}~%";char*b=/*
)(setq a "\\\"',s='\\\\")
(setq */ "
t(setq /*;*/){}main(){char q='%c%c',s='%c%c';char*a=
%c%s%c;char*b=/*
)(setq a %c%c%c%c%c',s='%c%c%c%c%c)
(setq */ %c%s%c;printf(b,s,q,s,s,q,a,q,q,s,s,s,q,s,s,s,s,q,q,b,q/*
)(format t /* a /* a */);}
";printf(b,s,q,s,s,q,a,q,q,s,s,s,q,s,s,s,s,q,q,b,q/*
)(format t /* a /* a */);}