Programs that print their own source code

[Meteorswarm]

Yeah, on Ubuntu Lucid it still fails:

Code: Select all

alec@Kongming:~$ echo '#!md5sum' > md5
alec@Kongming:~$ chmod +x md5
alec@Kongming:~$ ./md5
bash: ./md5: md5sum: bad interpreter: No such file or directory
alec@Kongming:~$


[Goplat]

Use the absolute path. "#!/usr/bin/md5sum" or wherever it is. (If you don't know, run "which md5sum".)

[RoadieRich]

Works on OS-X/darwin too...

Code: Select all

$ echo '#!'`which md5sum` > md5
$ chmod +x md5
$ ./md5
3190365db110e56a2bc307f24e383685  ./md5
$


(I was kinda surprised that "$ echo '#!'`which md5sum`" worked as I expected it to, though.)

[TheChewanater]

Works on iPhone/Darwin as well with a terminal emulator.

[ircmaxell]

A little bit of php that uses eval() (a slight cheat) and self-modifies its code. Each time, it generates random variable names... Run it as `php -q test.php | php -q | php -q | php -q | php -q` The -q flag is needed to suppress the content-type header that php wants to include normally...

Code: Select all

<?php

$var='
class Replace {

        public function __construct($string) {
                $this->source = $string;
        }

        public function __toString() {
                return $this->makeSource();
        }

        protected function makeSource() {
                $body = "<?php\n\n\$var=\'".addcslashes($this->source,"\'")."\';\n\necho eval(\$var);\n";
                if (preg_match_all("#\\\$(this->[a-zA-Z][a-zA-Z0-9_]*|[a-zA-Z][a-zA-Z0-9_]*)(\.|\s|\))#", $body, $matches, PREG_SET_ORDER)) {
                        $vars = array();
                        foreach ($matches as $match) {
                                $vars[] = $match[1];
                        }
                        array_unique($vars);
                        foreach ($vars as $var) {
                                if ($var == "this") continue;
                                $name = $this->createRandomName();
                                if (strpos($var, "->") !== false) {
                                        $replace = "\$this->".$name;
                                } else {
                                        $replace = "\$".$name;
                                }
                                $body = str_replace("\$".$var, $replace, $body);
                        }
                }
                return $body;
        }

        protected function createRandomName() {
                $returnLen = rand(5, 15);
                $chrs = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_";
                $maxchr = strlen($chrs) - 1;
                $return = "";
                for ($i = 0; $i < $returnLen; $i++) {
                        $return .= $chrs[rand(0, $maxchr)];
                }
                return $return;
        }
}

return new Replace($var);';

echo eval($var);



[Meteorswarm]

Use the absolute path. "#!/usr/bin/md5sum" or wherever it is. (If you don't know, run "which md5sum".)

Ah, yes, that does it.

Along the original lines, a shorter program to print its own source would be

Code: Select all

#!/bin/cat

possibly without the /bin, but I need the /bin on my system.

[DharmaBum]

If anyone writes a quine in Brainfuck they win the internet. Shouldn't be impossible considering it's basically a language for writing Turing Machines.

Another one that would surely yield hilarity is LOLCODE.

[hotaru]

If anyone writes a quine in Brainfuck they win the internet. Shouldn't be impossible considering it's basically a language for writing Turing Machines.

of course it isn't impossible.

Another one that would surely yield hilarity is LOLCODE.

something like this?

[Pesto]

This thread inspired me to implement my own programming language, called quine. In quine, every program is a quine. The syntax is quite simple, as any ASCII text file is a valid program.

You can install my quine interpreter on any Linux machine with the following command.

Code: Select all

alias quine='cat'

I have not yet had time to start work on porting this to Windows or other operating systems.

[TheChewanater]

You should continue work on ports to other platforms. However, I understand how hard it is writing a new language, which I would never even attempt myself. Hopefully popular libraries will start supporting it soon and it can take off.

[hotaru]

I have not yet had time to start work on porting this to Windows or other operating systems.

windows already includes an interpreter. it's called "type".

[skeptical scientist]

If you think using the repr() function is cheating, feel free to post an alternative.

It's totally cheating!

Here's a Python quine I just wrote. I didn't know the repr() function, so I wrote a function to duplicate enough of it's behavior for the quine. Unfortunately, that makes the code a fair bit longer.

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# Simple Python program to print its own source

def sanitize(s): #turns a string into python input representing the same string
    s=list(s)
    l=0
    while l<len(s):
        if s[l]=='\n':
            s=s[:l]+['\\','n']+s[l+1:]
            l+=2
        elif s[l]=='\\':
            s=s[:l]+['\\','\\']+s[l+1:]
            l+=2
        elif s[l]=='\"':
            s=s[:l]+['\\','\"']+s[l+1:]
            l+=2
        else: l+=1
    s=reduce(lambda x,y:x+y,s)
    return s

s1,s2="# Simple Python program to print its own source\n\ndef sanitize(s): #turns a string into python input representing the same string\n    s=list(s)\n    l=0\n    while l<len(s):\n        if s[l]=='\\n':\n            s=s[:l]+['\\\\','n']+s[l+1:]\n            l+=2\n        elif s[l]=='\\\\':\n            s=s[:l]+['\\\\','\\\\']+s[l+1:]\n            l+=2\n        elif s[l]=='\\\"':\n            s=s[:l]+['\\\\','\\\"']+s[l+1:]\n            l+=2\n        else: l+=1\n    s=reduce(lambda x,y:x+y,s)\n    return s\n\ns1,s2=\"","\"\ns=s1+sanitize(s1)+'\",\"'+sanitize(s2)+s2\nprint s"
s=s1+sanitize(s1)+'","'+sanitize(s2)+s2
print s


[thoughtfully]

Here's how to really cheat in Python.

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0 % cat cheat.py; python cheat.py
print open(__file__).read()
print open(__file__).read()


[Cosmologicon]

We still doing this? Here's my python one-liner:

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print (u"*3)[46:-9].replace(chr(117),chr(117)+chr(34)) print (u"*3)[46:-9].replace(chr(117),chr(117)+chr(34))

[PM 2Ring]

We still doing this?

I suspect that skeptical scientist has revived this thread because he's just started learning Python. If so, yay!

Here's my python one-liner:

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print (u"*3)[46:-9].replace(chr(117),chr(117)+chr(34)) print (u"*3)[46:-9].replace(chr(117),chr(117)+chr(34))

I'll pay that.

[skeptical scientist]

I suspect that skeptical scientist has revived this thread because he's just started learning Python. If so, yay!

Indeed. The academic job market is really tough right now, and I'm thinking about getting a job as a programmer. Any suggestions? (Probably not in this thread - if there's a relevant thread I should look at, a link would be nice.)

Here's my python one-liner:

Code: Select all

print (u"*3)[46:-9].replace(chr(117),chr(117)+chr(34)) print (u"*3)[46:-9].replace(chr(117),chr(117)+chr(34))

That's cute. I like how you need basically two copies of your string, but you take three and slice to get the right start/stop point.

[WarDaft]

Job suggestions, language suggestions, or other?

[skeptical scientist]

Job suggestions, language suggestions, or other?

OT stuff taken here.

[tastelikecoke]

I've been playing with Quines in python recently. The first quine I coded is not short at all, so I tried again.

Code: Select all

s = """s =
print s[:4]+chr(34)+chr(34)+chr(34)+s+chr(34)+chr(34)+chr(34)+s[4:]"""
print s[:4]+chr(34)+chr(34)+chr(34)+s+chr(34)+chr(34)+chr(34)+s[4:]

[RAKtheUndead]

As far as I'm concerned, quines have been uninteresting since 1994, when this was done:

http://www.ioccc.org/1994/smr.hint

I think he told Common Lisp to shove it.

[sourmìlk]

I was just about to bring that up