#! /bin/bash

number=$1

if [ $number -lt  0 -o $number -gt 999 ]
then
    echo put the right input between 0 and 999
fi

case "$number"
    [0-9])

output=""
if [[ "$number" -gt 100 ]]; then
    # okay, we know $number is greater than 100
    hundreds=$((number/100))
    case $hundreds in
        1) output="one" ;;
        2) output="two" ;;
        3) output="three" ;;
        # et cetera
    esac
    number=$((number-100*hundreds))
fi
output="$output hundred"