#!/bin/bash
circled_digit() {
circled_digits='⓪①②③④⑤⑥⑦⑧⑨⑩⑪⑫⑬⑭⑮⑯⑰⑱⑲⑳'
if [ $1 -lt 20 ] 2>/dev/null ; then
printf '%b' "${circled_digits:$1:1}\n"
else
printf '%b' "Must give a number between 0 and 20. Not '$1'\n"
fi
}
circled_digit $1