Arrays in Shell Script, not Bash

Question

I am probably just having a brain fart, but I can not for the life of me figure out how to loop through an array in shell script, not bash. Im sure the answer is on stackoverflow somewhere already, but I can not find a method of doing so without using bash. For my embedded target system bash is not currently an option. Here is an example of what I am attempting to do and the error that is returned.

#!/bin/sh

enable0=1
enable1=1

port=0
while [ ${port} -lt 2 ]; do
    if [ ${enable${port}} -eq 1 ]
        then
        # do some stuff
    fi

    port=$((port + 1))
done

Whenever I run this script the error "Bad substitution" is returned for line with the if statement. If you guys have any ideas I would greatly appreciate it. Thanks!

Answer 1

a="abc 123 def"

set -- $a
while [ -n "$1" ]; do
    echo $1
    shift
done

Output via busybox 1.27.2 ash:

abc
123
def