Happy birthday in bash

Usage: hbd.sh [NAME] [AGE]

Requirements: GNU Bash
              POSIX bc (preferably GNU bc)

hbd.sh is licensed under the Eiffel Forum License version 2.

hbdmusic.sh and korobeiniki.sh are licensed under the
GNU General Public License version 3 or (at your option) any
later version published by the Free Software Foundation.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.