Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
throw=0
zeroes=0
ones=0
twos=0
threes=0
fours=0
fives=0
sixes=0
# Throw count.
# Must initialize counts to zero.
# since an uninitialized variable is null, not zero.
print_result ()
{
echo
echo "ones = $ones"
echo "twos = $twos"
echo "threes = $threes"
echo "fours = $fours"
echo "fives = $fives"
echo "sixes = $sixes"
echo
}
update_count()
{
case "$1" in
0) let "ones += 1";; # Since die has no "zero", this corresponds to 1.
1) let "twos += 1";; # And this to 2, etc.
2) let "threes += 1";;
3) let "fours += 1";;
4) let "fives += 1";;
5) let "sixes += 1";;
esac
}
echo
while [ "$throw" −lt "$MAXTHROWS" ]
do
let "die1 = RANDOM % $PIPS"
update_count $die1
let "throw += 1"
done
print_result
# The scores should distribute fairly evenly, assuming RANDOM is fairly random.
# With $MAXTHROWS at 600, all should cluster around 100, plus−or−minus 20 or so.
#
# Keep in mind that RANDOM is a pseudorandom generator,
# and not a spectacularly good one at that.
# Exercise (easy):
# −−−−−−−−−−−−−−−
# Rewrite this script to flip a coin 1000 times.
# Choices are "HEADS" or "TAILS".
exit 0
As we have seen in the last example, it is best to "reseed" the RANDOM generator each time it is invoked.
Using the same seed for RANDOM repeats the same series of numbers. (This mirrors the behavior of the
Chapter 9. Variables Revisited 99