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2011-03-12 - Confoo 2011 presentation
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True Random Dice Roll

Terminal - True Random Dice Roll
echo $((0x$(head -c5 /dev/random|xxd -ps)%6+1))
2012-09-21 02:16:42
User: atoponce
Functions: echo head
True Random Dice Roll

/dev/random is said to by cryptographically secure, and unpredictable, as it gathers data from external sources, influenced by human timing interactions with computers, to fill the entropy pool. As such, this is a quick way to do a true random fair-6 dice roll. Using this method, you could easily create passphrases with Diceware http://diceware.com.

for i in {1..5}; do echo -n $((0x$(head -c5 /dev/random|xxd -ps)%6+1)); done; echo


There are 2 alternatives - vote for the best!

Terminal - Alternatives
echo $(</dev/urandom tr -dc 1-6 | head -c1)

Know a better way?

If you can do better, submit your command here.

What others think

Hmmm. Not quite true random. From one byte of randomness mod 6 there are 43 possible 0-3s and only 42 possible 4-5s - therefore your die is weighted against fives and sixes. Perhaps echo $(

Comment by unixmonkey40000 134 weeks and 1 day ago

You are absolutely right. However, it's biased away from 5 and 6 by 2 percent. So, you could update the command to read more bytes. Reading 2 bytes would produce a bias away from 5 and 6 by 9 thousandths of one percent. Reading 3 bytes would produce a bias away from 5 and 6 of 4 one-hundred thousandths by one percent. I would be willing to bet that standard fabricated dice have a larger bias towards some numbers than that. So, for practical purposes, reading only 10 bytes, would be more than sufficient, and certainly "close enough". I've updated the post.

Comment by atoponce 134 weeks ago

Your point of view

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