Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
Diamonds
Hearts
Spades"
Denominations="2
3
4
5
6
7
8
9
10
Jack
Queen
King
Ace"
suite=($Suites)
denomination=($Denominations)
# Read into array variable.
num_suites=${#suite[*]} # Count how many elements.
num_denominations=${#denomination[*]}
echo −n "${denomination[$((RANDOM%num_denominations))]} of "
echo ${suite[$((RANDOM%num_suites))]}
# $bozo sh pick−cards.sh
# Jack of Clubs
# Thank you, "jipe," for pointing out this use of $RANDOM.
exit 0
Jipe points out another set of techniques for generating random numbers within a range.
# Generate random number between 6 and 30.
rnumber=$((RANDOM%25+6))
# Generate random number in the same 6 − 30 range,
#+ but the number must be evenly divisible by 3.
rnumber=$(((RANDOM%30/3+1)*3))
# Exercise: Try to figure out the pattern here.
Just how random is $RANDOM? The best way to test this is to write a script that tracks the distribution of
"random" numbers generated by $RANDOM. Let's roll a $RANDOM die a few times...
Example 9−25. Rolling the die with RANDOM
#!/bin/bash
# How random is RANDOM?
RANDOM=$$
PIPS=6
MAXTHROWS=600
# Reseed the random number generator using script process ID.
# A die has 6 pips.
# Increase this, if you have nothing better to do with your time.
Chapter 9. Variables Revisited 98