Just a small script ;)

#!/usr/bin/perl

Entropy H({x_1,…,x_n}) of random variable X={x_1,…,x_n}

H(X) := -\sum_{i=1}^{n} p(x_i) log_b p(x_i)

H(x) ~ Thermodynamic entropy with k_b = 1

extract distribution of random variable X

while () { $nx{$_}++ foreach (split //); } $n += $_ foreach (values %nx);

calculate entropy

foreach my $x (keys %nx)
{
my $px = $nx{$x} / $n;
$H -= $px * log($px);
}
$H /= log(2);
printf “Entropy %.2f bits (total bytes %d)\n”, $H, $n;