convert decimal to hexadecimal

hexnote.sh

#!/bin/bash -
#
# SCRIPT: hexnote
# AUTHOR: Luciano D. Cecere
########################################################################
#
# hexnote - convert base 10 integers to hexadecimal notation
# Copyright (C) 2015 Luciano D. Cecere <ldante86@aol.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version.
#
# 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.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
########################################################################

export PATH=/bin:/usr/bin
unalias -a
PROGRAM="${0##*/}"

base16=( {0..10} {A..F} )

_main()
{
    dec="$1" digit= size= hex=

    while [ $dec -ne 0 ]
    do
      ((digit=dec % 16))
      if [ $digit -ge 10 ]; then
        hex=${base16[digit+1]}${hex}
      else
        hex=${base16[digit]}${hex}
      fi
      ((dec/=16))
    done

    echo ${hex}
}

[ $# -eq 0 ] && echo "Usage: $PROGRAM [-l] numbers"

while [ $# -ne 0 ]
do
  case $1 in
   -l)
     base16=( {0..10} {a..f} )
     ;;
    0)
     echo 0
     ;;
    *.*|*[a-z]*|*[A-Z]*|-*|0*)
    true
    ;;
    *)
    _main "$1"
    ;;
  esac
  shift
done