#!/bin/bash

FRIEND="world"

usage() {
    cat <<- EOF
Usage: $0 [OPTION]...
Greets the given friend.

With no friend provided, prints "Hello, world!"

  -f, --friend             set the name of the friend to greet
  -h, --help               print this help text
EOF
}

# parse argv variables
while [ "$#" -gt 0 ]; do

  case "$1" in
  -f | --friend)
    FRIEND="$2"
    shift 2
    ;;

  -f=* | --friend=*)
    FRIEND="${1#*=}"
    shift 1
    ;;

  -h | --help)
    usage
    exit 0
    ;;

  *)
    echo "Unrecognized argument ${1#*=}"
    echo
    usage
    exit 1
    ;;
  esac

done

echo "Hello, $FRIEND!"