Linux script using a Hardware (True) Random number generator

Question

I'd like to use the built in hardware random number generator in my RPI3 for a project. Currently I'm only able to use /dev/hwrng to save binary dumps with

dd if=/dev/hwrng of=data.bin bs=25 count=1

What I need for my project is to read 200 bit long data chunks from the random source (/dev/hwrng) with a frequency of 1 reading/second and count the 1's in it and write the result as decimal into a text file with a timestamp, like this:

datetime, value 11/20/2018 12:48:09, 105 11/20/2018 12:48:10, 103 11/20/2018 12:48:11, 97

The decimal number should be always close to 100, since it is a random data source and the expected number of 1's and 0's should be the same. Any help is appreciated....

I did come up wit a perl script that is close to what I wan't, so let me share it. I'm sure it could be done in a much cleaner way though...

#!/usr/bin/perl
use strict;
use warnings;
use DateTime;
my @bitcounts = (
   0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 
   3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 
   3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 1, 2, 
   2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 
   3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 
   5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 
   2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 
   4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 
   3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 2, 3, 3, 4, 3, 4, 
   4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 
   5, 6, 6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 4, 5, 
   5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
);

for (my $i=0; $i <= 10; $i++) {
system("dd if=/dev/hwrng of=temprnd.bin bs=25 count=1 status=none");
my $filename = 'temprnd.bin';
open(my $fh, '<', $filename) or die "$!";
binmode $fh;
my $count = 0;
my $byte  = 0;
while ( read $fh, $byte, 1 ) {
   $count += $bitcounts[ord($byte)];
}
my $dt = DateTime->now;
print join ',', $dt->ymd, $dt->hms,"$count\n";
system("rm temprnd.bin");
sleep 1;
}
__END__

Answer 1

Try running the following code

for ((n=0; n<200; ++n)); do echo $(date '+%m/%d/%Y %H:%M:%S'), $(od -vAn -N1 -tu1 < /dev/hwrng); sleep 1; done

If you want to save it to a file, add simple redirect in the end > somefile

Updating on the new request, try running the following code

for ((n=0; n<10; ++n)); do
    count=0
    for ((s=0; s<200; ++s)); do
        if (( $(od -vAn -N1 -tu1 < /dev/hwrng) > 127 )); then ((++count)); fi
    done
    echo $(date '+%m/%d/%Y %H:%M:%S'), $count
    sleep 1
done