Quine

Print out a program's own source code. Since this is a puzzle, shorter/more efficient versions are encouraged along side more obvious versions.

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Ada

with Text_Io;
procedure Self is 
   Q:Character:='"';
   A:String(1..132):="with text_io;procedure self is q:character:=;a:string(1..132):=;begin text_io.put_line(a(1..45)&q&a(46..65)&q&a&q&a(66..132));end;"; begin 
   Text_Io.Put_Line(A(1..45)&Q&A(46..65)&Q&A&Q&A(66..132));
end;

The code space is also the data space of a Befunge program. Programs can be read and modified on the fly. This quine works by reading and printing each character of the source. (This is a implicit loop, since the Befunge codespace wraps around.)

:0g,:66+`#@_1+

Forth

SOURCE TYPE

Haskell

The obvious solution, as a one-liner:

let q s = putStrLn $ s ++ show s in q "let q s = putStrLn $ s ++ show s in q "

Having the string at the end makes things a bit simpler than in generic version mentioned in the Wikipedia article.

Haskell does not keep the code in an uncompiled-equivalent form around at runtime, so the "quotation trick" has to be used.

Java

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class Quine{
	public static void main(String[] args){
		try{
			BufferedReader input = new BufferedReader(
					new FileReader("Quine.java"));
			String line;
			while((line = input.readLine())!=null){
				System.out.println(line);
			}
		}catch(FileNotFoundException e){
			e.printStackTrace();
		}catch(IOException e){
			e.printStackTrace();
		}
	}
}

Perl

This example retrieves the name of the source file from the $0 variable, which represents the file path and name used to invoke the script.

#!/usr/bin/perl
open FILE, "< $0" or die "Failed to open self\n";
map { print $_ } <FILE>;
close FILE;

Assuming the code is saved in the file quine.pl, this works when executed as

./quine.pl

or

perl quine.pl

but fails when fed to the perl interpreter's standard input as

cat quine.pl|perl

If we may assume that the source file is named "quine.pl", replacing

open FILE, "< $0" or die "Failed to open self\n";

with

open FILE, "< quine.pl" or die "Failed to open self\n";

will allow us to execute the code through the interpreter's standard input:

cat quine.pl|perl

PHP

This example obtains its own filename from the __FILE__ built-in variable.

<?
$fh = fopen( __FILE__, 'r' );
echo fread($fh, filesize(__FILE__));
fclose( $fh );
?>

Strictly speaking, however, the example prints more than its own source code. Because PHP is designed to service HTTP requests, the output looks like this:

X-Powered-By: PHP/5.2.3-1ubuntu6
Content-type: text/html

<?
$fh = fopen( __FILE__, 'r' );
echo fread($fh, filesize(__FILE__));
fclose( $fh );
?>

(The X-Powered-By line will vary from system to system.)

Seed7

$ include "seed7_05.s7i";
const array string: prog is [](
"$ include \"seed7_05.s7i\";",
"const array string: prog is [](",
"const proc: main is func",
"  local var integer: number is 0;",
"  begin",
"    for number range 1 to 2 do writeln(prog[number]); end for;",
"    for number range 1 to 11 do",
"      writeln(literal(prog[number]) <& \",\");",
"    end for;",
"    writeln(literal(prog[12]) <& \");\");",
"    for number range 3 to 12 do writeln(prog[number]); end for;",
"  end func;");
const proc: main is func
  local var integer: number is 0;
  begin
    for number range 1 to 2 do writeln(prog[number]); end for;
    for number range 1 to 11 do
      writeln(literal(prog[number]) <& ",");
    end for;
    writeln(literal(prog[12]) <& ");");
    for number range 3 to 12 do writeln(prog[number]); end for;
  end func;

Original source: [1]

UNIX Shell

#!/bin/sh
cat "$0"