#!/bin/dash

# written by andrewt@unsw.edu.au for COMP(2041|9044)
# print print numbers < 1000

# note use of local Shell builtin to scope a variable
# without the local declaration
# the variable i in the function would be global
# and would break the bottom while loop

# local is not (yet) POSIX but is widely supported

is_prime() {
    local n i
    n=$1
    i=2
    while test $i -lt $n
    do
        test $((n % i)) -eq 0 &&
            return 1
        i=$((i + 1))
    done
    return 0
}

i=0
while test $i -lt 1000
do
    is_prime $i &&
        echo $i
    i=$((i + 1))
done