#!/bin/bash

chars=(0 1 2)
maxchars=2

function permute {
	[[ -z $nchar ]] && echo permute function needs nchar variable && exit 1
	local charvar=char$nchar

	for char in ${chars[@]}; do
		eval $charvar=$char

		if (( nchar >= maxchars )); then
			tmp=1
			until (( tmp > maxchars )); do
				var=char$tmp
				echo -n ${!var}
				(( tmp++ ))
			done; unset tmp var
			echo
		else
			(( nchar++ ))
			permute
		fi
	done
	(( nchar-- ))
}

nchar=1
permute