mirror of https://github.com/tLDP/LDP
69 lines
1.5 KiB
Bash
69 lines
1.5 KiB
Bash
#!/bin/bash
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# How random is RANDOM?
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RANDOM=$$ # Reseed the random number generator using script process ID.
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PIPS=6 # A die has 6 pips.
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MAXTHROWS=600 # Increase this, if you have nothing better to do with your time.
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throw=0 # Throw count.
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ones=0 # Must initialize counts to zero,
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twos=0 #+ since an uninitialized variable is null, not zero.
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threes=0
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fours=0
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fives=0
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sixes=0
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print_result ()
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{
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echo
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echo "ones = $ones"
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echo "twos = $twos"
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echo "threes = $threes"
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echo "fours = $fours"
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echo "fives = $fives"
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echo "sixes = $sixes"
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echo
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}
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update_count()
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{
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case "$1" in
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0) let "ones += 1";; # Since die has no "zero", this corresponds to 1.
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1) let "twos += 1";; # And this to 2, etc.
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2) let "threes += 1";;
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3) let "fours += 1";;
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4) let "fives += 1";;
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5) let "sixes += 1";;
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esac
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}
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echo
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while [ "$throw" -lt "$MAXTHROWS" ]
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do
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let "die1 = RANDOM % $PIPS"
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update_count $die1
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let "throw += 1"
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done
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print_result
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# The scores should distribute fairly evenly, assuming RANDOM is fairly random.
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# With $MAXTHROWS at 600, all should cluster around 100, plus-or-minus 20 or so.
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#
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# Keep in mind that RANDOM is a pseudorandom generator,
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#+ and not a spectacularly good one at that.
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# Randomness is a deep and complex subject.
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# Sufficiently long "random" sequences may exhibit
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#+ chaotic and other "non-random" behavior.
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# Exercise (easy):
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# ---------------
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# Rewrite this script to flip a coin 1000 times.
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# Choices are "HEADS" and "TAILS".
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exit 0
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