freebsd-dev/tools/test/devrandom/stat.8bit

#!/usr/bin/perl

#
# Perform primitive binning into 8-bit bins (take 8 bits of randomness
# at a time) and see if the distribution is flat. The output should be
# checked by eye - are all the numbers roughly the same?
#
# Redirect the output from this to a file - and make a cup of coffee while
# it runs. This program is a CPU Hog!
#
# $FreeBSD$
#

for ($i = 0; $i < (1024*32); $i++) {
	open(BIN, "/dev/urandom") || die "Cannot open /dev/urandom - $!\n";
	$len = sysread(BIN, $a, 256);
	close(BIN);
	if ($len > 0) {
		for ($j = 0; $j < $len; $j++) {
			$k = unpack("C", substr($a, $j, 1));
			$bin[$k]++;
		}
	}
}

for ($i = 0; $i < 256; $i++) {
	printf("%.2X ", $bin[$i]);
}
printf "\n";