using /dev/(u)random for seed ?

PTBmilo · 04-14-2003, 05:53 PM

What is a good way to do this? this is what I'm trying (c++):

Code:

        ifstream randomStream;
        randomStream.open("/dev/random");
        char randomDataString [201];
        randomStream.getline(randomDataString,200);

And then I try to conver the string to a number with some gmp functions. I can print out the datastring, but I can only get '0' when I convert it to an integer.

I can make integers with regular character strings, but this one won't work. Are there any other ways of doing this?

Tinkster · 04-14-2003, 08:29 PM

Not quite sure why you'd want to read a 200
characters from the device ... what are you
trying to achieve?

One "normal approach" in using it would be
to read ONE byte from it, and use that as an
integer as a seed for srand()...
Or, if you want repeated random numbers from
0 to 254, repeatedly read ONE byte ...

Cheers,
Tink

PTBmilo · 04-15-2003, 01:19 AM

Thanks this is how I ended up doing it:

Code:

int getRandomInt()
{
        ifstream randomStream;
        randomStream.open("/dev/urandom");
        if(randomStream.fail())
        {
                cout << "Can't open /dev/urandom\n";
                exit (1);
        }
        char randomChar;
        randomStream.get(randomChar);

        int randomInt;
        randomInt = int(randomChar);

        randomStream.close();

return randomInt;
}

Then use that for a seed. It's not for anything important, I'm just playing around w/ the gmp library. I wanted to use a big ass binary string for the initial seed, but something wasn't flying.