How to write a single-line password generator

Question

Is there a way of writing a password generator in only one line?

The password should consist of 8 random chars out of a-z, A-Z and 0-9.

Example: This is one attempt I made in PHP!

echo substr(str_shuffle(implode('', array_merge(range(0,9), range('a','z'), 
    range('A','Z')))), 0, 8);

Answer 1

BASH^*

Simple and cute:

</dev/urandom tr -dc [:alnum:] | head -c8  

for all locales, or

</dev/urandom tr -dc a-zA-Z0-9 | head -c8  

for ASCII only.

^{* Just unix shell commands actually}

Answer 2

$s=implode('',array_rand(array_flip(array_merge(range('a','z'),range('A','Z'),range('0','9'))),8));

It has the same issue, that it won't repeat characters. But at least it works :P

Now this version does as asked, and repeats characters:

while(strlen($s.=array_rand(array_flip(array_merge(range('a','z'),range('A','Z'),range('0','9')))))<8){}

Answer 3

C#

Guid.NewGuid();

This should work :)

Ok, fitting in the rules:

Guid.NewGuid().ToString("N").Substring(0, 8);

_{Nice hint David}

Answer 4

Python (93 92 91 87 82 chars)

z=__import__;''.join(z('random').choice(z("string").printable[:62]) for x in'.'*8)    

Answer 5

$pass = substr(md5(rand()), 0, 8);

Answer 6

Python

"".join(__import__('random').sample(__import__('string').printable[:62],8))

Answer 7

JavaScript. I've made two, although I allow all 62 characters between A and ~.

(function(n){return eval("["+Array(n).join("String.fromCharCode(65+~~(Math.random()*61)),")+",'']").join("");}(8));

And:

(function(n,p){while(n--){p+=String.fromCharCode(65+~~(Math.random()*61))}return p;}(8,""));

Answer 8

Easy.

function securityismymiddlename() {return 'password';}

Answer 9

J, 29 characters

a.{~(+48 55 61{~9 35&I.)?8$62

Answer 10

Windows Powershell

 (1..8 | % { [char](( ('0','9'),('A','Z'),('a','z')) | % { [char]$_[0]..[char]$_[1] } )[(random)%62] }) -join ""

94 Characters, technically one line of code.

With formatting:

 (1..8 | 
    % { 
        [char](
                ( 
                    ('0','9'),
                    ('A','Z'),
                    ('a','z')
                 ) | 
                 % { 
                    [char]$_[0]..[char]$_[1] 
                   } 
             )[(random)%62] 
          }
   ) -join ""

Answer 11

Javascript

44 chars

This one is fairly short but does not include capital letters. I posted it because I just like it the way it is. ;P

alert(Math.random().toString(36).substr(2));

Try it out here: http://jsfiddle.net/ReYjF/

Answer 12

Yet another one in Ruby - only core lib and the shortest!

(0..7).map{[*?a..?z,*?A..?Z,*?0..?9].sample}.join

A version that never uses the same char twice:

[*?a..?z,*?A..?Z,*?0..?9].sample(8).join

edit: shaved off two more chars.

(0..7).map{(?0..?z).grep(/[\w\d]/).sample}.join

Answer 13

I'll give it a shot

for($c=array_merge(range(0,9),range('A','Z'),range('a','z'));strlen($p.=$c[array_rand($c)])<8;);

edit: and here's another one:

substr(preg_replace('/[^[:alnum:]]/','',crypt(uniqid(),'lr')),-8);

Answer 14

PHP:

Here's one that writes out in one line in PHP. But it can only output passwords with lowercase alphabet characters and numbers.

echo "Here's your password: " . substr(md5(strval(time())), 0, 8);

Answer 15

BASH^*

Another one for shell:

date | md5sum | base64 | cut -c-8

^{* Just unix shell commands actually}

Answer 16

Groovy

(0..7).collect{(('a'..'z')+('A'..'Z')+(0..9))[new Random().nextInt(62)]}.join()

I knew Ruby and Groovy had much in common but the likeness of the solutions are even closer than I would have thought.

Answer 17

PHP, Follows rules perfectly

<? 
echo substr(str_replace(array('/','+','='),'',base64_encode(md5(time()))), 0, 8); 
?>

Answer 18

PHP, Here's another PHP solution that follows the rules exactly, this one might be 'more random' too.

<? echo substr(str_shuffle(str_repeat('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',8)), 0, 8);?>

Answer 19

echo implode('', array_map(function () { return substr('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPRSTUVWXYZ0123456789', mt_rand(0, 64), 1); }, range(1, 8)));

Answer 20

Javascript:

alert((function(i) {return ((i < 7) ? arguments.callee(++i) : '') + (Math.round(Math.random() * 1) == 1 ? (Math.round(Math.random() * 1) == 1 ? String.fromCharCode(65 + Math.round(Math.random() * 25.5)) : String.fromCharCode(97 + Math.round(Math.random() * 25.5))) : String.fromCharCode(48 + Math.round(Math.random() * 9.5))) + ''}).call(this, 0))

Because I like recursion and Javascript and I don't consider a loop construct to be "one" line.

I suspect it is more likely to generate numbers than letters though.... Fortunately, it restricts itself to lowercase and uppercase letters and numbers only.

Answer 21

for($i=0;$i<8;$i++){$p.=array_rand(array_flip(array(chr(rand(48,57)),chr(rand(65,90)),chr(rand(97,122)))));}

echo $p;

Answer 22

C#

DateTime.Now.ToString("r").Replace(",", "").Replace(" ", "").Replace(":", "").Substring(0,8);

output:
"r" = Thu, 10 Mar 2011 00:48:06 GMT
password: Thu10Mar

That's obviously only useful once a day. More random:

DateTime.Now.ToString("ddd") + DateTime.Now.Ticks.ToString().Substring(DateTime.Now.Ticks.ToString().Length -2) + DateTime.Now.ToString("MMM");

output:
Thu81Mar

Answer 23

Perl, from command-line:

perl -e '@r=(a..z,A..Z,0..9);$p.=$r[int(rand(@r))],$i++while($i<8);print"$p\n"'

Answer 24

C

123 bytes, excluding #include lines.

int r,i;main(){srand(time(0));while(++i<9){r=rand()%62;if(r>35)r+=61;else if(r>9)r+=55;else r+=48;putchar(r);}putchar(10);}

Properly formatted:

#include <stdio.h>
#include <stdlib.h>

int r, i;

main() {
    srand(time(0));

    while (++i < 9) {
        r = rand() % 62;

        if (r > 35)
            r += 61;
        else if (r > 9)
            r += 55;
        else
            r += 48;

        putchar(r);
    }

    putchar(10);
}

Of course, you would want to use random() instead of rand() in a real application. I'm just shaving bytes.

Also, since 62 is not a power of 2, using mod slightly favors '0' and '1'.

EDIT:

Using the ternary operator (after muntoo's answer), 101 bytes:

int r,i;main(){srand(time(0));while(++i<9)putchar((r=rand()%62)<10?r+48:r<36?r+55:r+61);putchar(10);}

Answer 25

C++, 77

for(char i=0,r;i<8;i++)std::cout<<char((r=rand()%62)<10?r+48:r<36?r+55:r+61);

---

Full program:

#include <iostream>
#include <time.h>

int main(int argc, char* argv[])
{
    for(char i=0,r;i<8;i++)std::cout<<char((r=rand()%62)<10?r+48:r<36?r+55:r+61);

    std::cin.ignore();

    return(0);
}

---

For some reason, this doesn't run as expected:

for(char i=0,r;i<8;i++,srand(time(0)))std::cout<<(char)(((r=rand()%62)<10)?r+48:r<36?r+55:r+61);

Answer 26

Python (72 67 54 chars)

`__import__('random').random()`.encode("base64")[3:11]

Answer 27

Considering that security should be the upmost priority, and someone may stumble across this thread and actually try to use the code here (the horror), I feel this answer is appropriate:

Use A Library!!!

In PHP, You could use the GenPhrase Library:

PHP (37 characters)

(new GenPhrase\Password)->generate();

That will generate a word list (longer than 8 characters) with a minimum of 50 bits of entropy...

Answer 28

Here's another in Python, pulling one from gnibbler above...

__import__('base64').b64encode(str(__import__('random').getrandbits(256)))[:8]

I would like to be able to get a random 8 character slice of the string generated from b64encode(). Anyone know how to do that in one line?

You could use urlsafe_b64encode() if you want to avoid + and / characters...

Answer 29

C#

string password = new String(Enumerable.Range('0', 'z'-'A'+1).Select(i => (char)i).Where(i => char.IsLetterOrDigit(i)).OrderBy(i => Guid.NewGuid()).Take(8).ToArray());

Answer 30

C#

One-liner:

Func<string> newPassword = () => new string("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".Zip(Enumerable.Range(0, 62), Tuple.Create).Join(Enumerable.Range(0, 8).Select(r => Guid.NewGuid().ToString().Where(char.IsNumber).Select(Convert.ToInt32).Sum() % 62), o => o.Item2, i => i, (l, r) => l.Item1).ToArray());

Example app:

using System;
using System.Linq;

namespace ConsoleApplication36
{
    class Program
    {
        static void Main()
        {
            Func<string> newPassword = () => new string(
                "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
                .Zip(Enumerable.Range(0, 62), Tuple.Create)
                .Join(
                    Enumerable.Range(0, 8).Select(r => Guid.NewGuid().ToString().Where(char.IsNumber).Select(Convert.ToInt32).Sum() % 62),
                    o => o.Item2,
                    i => i,
                    (l, r) => l.Item1)
                .ToArray());

            Console.WriteLine(string.Join("\n", Enumerable.Range(0, 20).Select(c => newPassword())));
            Console.ReadKey();
        }
    }
}