Bash argument parser

bash_arg_parser.sh

#!/usr/bin/env bash
# This is comment from here: https://stackoverflow.com/a/28466267

parseArgs() {
  # just in case we call this twice make OPTIND local
  local OPTIND OPT
  
  die() { echo "$*" >&2; exit 2; }  # complain to STDERR and exit with error
  needs_arg() { if [ -z "$OPTARG" ]; then die "No arg for --$OPT option"; fi; }
  
  # Defaults (to be thorough, you could also assign alpha="" and charlie="")
  bravo="$HOME/Downloads"       # Overridden by the value set by -b or --bravo
  charlie_default="brown"       # Only set given -c or --charlie without an arg
  
  while getopts ab:c-: OPT; do  # allow -a, -b with arg, -c, and -- "with arg"
    # support long options: https://stackoverflow.com/a/28466267/519360
    if [ "$OPT" = "-" ]; then   # long option: reformulate OPT and OPTARG
      OPT="${OPTARG%%=*}"       # extract long option name
      OPTARG="${OPTARG#$OPT}"   # extract long option argument (may be empty)
      OPTARG="${OPTARG#=}"      # if long option argument, remove assigning `=`
    fi
    case "$OPT" in
      a | alpha )    alpha=true ;;
      b | bravo )    needs_arg; bravo="$OPTARG" ;;
      c | charlie )  charlie="${OPTARG:-$charlie_default}" ;;  # optional argument
      \? )           exit 2 ;;  # bad short option (error reported via getopts)
      * )            die "Illegal option --$OPT" ;;            # bad long option
    esac
  done
  shift $((OPTIND-1)) # remove parsed options and args from $@ list
}

parseArgs "$@"