Advanced Bash−Scripting Guide

fi
let "t += $i "
Primes[t]=$NON_PRIME
# Tag as non−prime all multiples.
done
let "i += 1"
done
Advanced Bash−Scripting Guide
}
# Invoke the functions sequentially.
initialize
sift
print_primes
# This is what they call structured programming.
echo
exit 0
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− #
# Code below line will not execute.
# This improved version of the Sieve, by Stephane Chazelas,
# executes somewhat faster.
# Must invoke with command−line argument (limit of primes).
UPPER_LIMIT=$1
let SPLIT=UPPER_LIMIT/2
# From command line.
# Halfway to max number.
Primes=( '' $(seq $UPPER_LIMIT) )
i=1
until (( ( i += 1 ) > SPLIT )) # Need check only halfway.
do
if [[ −n $Primes[i] ]]
then
t=$i
until (( ( t += i ) > UPPER_LIMIT ))
do
Primes[t]=
done
fi
done
echo ${Primes[*]}
exit 0
Compare this array−based prime number generator with an alternative that does not use arrays, Example
A−17.
−−
Chapter 26. Arrays 303