Shell Programming and Scripting

Hi,
I want a script of a code that will allow me to generate all possible combinations of alphanumberica characters of length 12 such that each string will contain numbers and either small or capital letters.
For example a string may look like this: 123AB45cd678.

I think you might want to rethink your post. Just using base36 numbers in bash to answer your post:

Code:

$ echo $((36#zzzzzzzzzzzz))
4738381338321616895

That is the largest 12 digit number in base36 - the gigantic number. It could easily take a desktop computer long time to count that high.
Every combination of base 36 number taken 12 at a time is much larger than the stupidly large number above.

I'm positive you need to tell us what you are trying to do, I've answered the question of how to print a decimal version base36 number, which is not what you asked. Mostly for completeness.

Code:

echo $((base#number))

Can you please tell us your requirement - example: generate 12 character passwords for linux.

Hi,
the number of all combinations from your condition is equal to 2.6543489742975863e+21
Where will you put everything? ...even if you will write in C...
set the condition exactly

@jim mcnamara & @nezabudka: Out of sheer curiosity - how did you derive those numbers? For me, the ASCII alphabet has 26 characters; upper case and lower case plus 10 digits makes that 62. 62^12=3,23e+21 - am I wrong?

Yes. I was mistaken I considered 61. I need to learn the alphabet

I just used bash to transform zzzzzzzzzzz, the highest value for 12 digits of base36, into decimal. It may not even be correct. Sorry for the confusion.

The idea of the OP's post seemed to be wildly unattainable with modern desktop hardware and/or required specialty software. Plus, where do you store the output? So I went with a quick version, since I do not have any bignum software on this box.

And base62 is correct, my explanation was for base64. I really was not clear.

Using {@,_} for "positions" 63 and 64 is bash behavior, I believe.

Note that there are only eleven z's in the string in red above; not twelve.

I thought most systems these days came with bc and/or dc.

Code:

$ echo '62 12^p' | dc
3226266762397899821056
$ echo '62^12' | bc
3226266762397899821056
$ 

Unfortunately, standard versions of bc are only required to handle input bases between 2 and 16 (inclusive) and dc isn't in the standards (but frequently has the same limits) so calculation in base 36 or base 62 aren't handled directly by these utilities. (On many systems, bc is implemented as a front-end to dc.) But from the above bc and dc output, I can say that 1000000000000 (base 62) (that is a digit 1 followed by twelve digit 0s) is 3226266762397899821056 (base 10).