bug#80661: questions about "shuf" utility

Mr. Eggert & colleagues,

I'm preparing an invited article for a medical journal on the topic of 
correct randomization for randomized controlled experiments and clinical 
trials.  I want to recomend the "shuf" utility for certain randomization 
tasks, because it is easy to use and widely available.

Before I can recommend shuf, however, I must confirm that it is free of 
several defects that are often found in other random permutation software. 
I'd be grateful if you would answer the following questions, providing 
pointers to relevant parts of the latest source code.  (I looked at the 
coreutils code myself, but I don't trust myself to unilaterally provide 
high-confidence answers to these questions.)

1. Can you confirm that shuf uses the Fisher-Yates/Durstenfeld unbiased 
shuffle algorithm?

2. Can you confirm that shuf avoids modulo bias --- the infamous and 
widespread bug, "random_number%N" --- when it makes equiprobable 
selections in its implementation of the shuffle algorithm?

3. Can you confirm that when shuf's "--random-source=FILE" option is used, 
the specified file is the sole source of random bits for all of shuf's 
behavior, and that if the same random source file is used again, holding 
all other shuf options & inputs constant, then shuf will emit the same 
output?

Many thanks in advance for your reply, and thank you for generously giving 
shuf to the world!  I'll do my best to find new users for shuf.

Finally, if you'd like to include in the "shuf" documentation a 
comprehensive discussion of the snafus that often arise in random 
permutation software, I recommend the following article:

https://spawn-queue.acm.org/doi/pdf/10.1145/3664645

Terence Kelly
tpkelly @ { acm.org, cs.princeton.edu, eecs.umich.edu }