Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
let SPLIT=UPPER_LIMIT/2
# Optimization:
# Need to test numbers only halfway to upper limit.
declare −a Primes
# Primes[] is an array.
initialize ()
{
# Initialize the array.
i=$LOWER_LIMIT
until [ "$i" −gt "$UPPER_LIMIT" ]
do
Primes[i]=$PRIME
let "i += 1"
done
# Assume all array members guilty (prime)
# until proven innocent.
}
print_primes ()
{
# Print out the members of the Primes[] array tagged as prime.
i=$LOWER_LIMIT
until [ "$i" −gt "$UPPER_LIMIT" ]
do
if [ "${Primes[i]}" −eq "$PRIME" ]
then
printf "%8d" $i
# 8 spaces per number gives nice, even columns.
fi
let "i += 1"
done
}
sift () # Sift out the non−primes.
{
let i=$LOWER_LIMIT+1
# We know 1 is prime, so let's start with 2.
until [ "$i" −gt "$UPPER_LIMIT" ]
do
if [ "${Primes[i]}" −eq "$PRIME" ]
# Don't bother sieving numbers already sieved (tagged as non−prime).
then
t=$i
while [ "$t" −le "$UPPER_LIMIT" ]
do
Chapter 26. Arrays 302