Bash 4.x Script to Show/ Hide Hidden Files in OSX

Tested on Yosemite with bash 4.3.33 (which was installed via homebrew, (http://johndjameson.com/blog/updating-your-shell-with-homebrew/).

#!/usr/bin/env bash
# A Bash 4.x Script to Show Hidden Files in OSX
#
function show_help() {
    >&2 echo "Please specify what I should do with hidden files:"
    >&2 echo -e "\tyes (show)"
    >&2 echo -e "\tno (don't show)"
}

if [[ $# < 1 ]] ; then
    show_help
    exit 1
fi
yes_or_no="${1^^}"
echo $yes_or_no
if [[ "${yes_or_no}" != @(YES|NO) ]]; then
    >&2 echo "Invalid argument '$1'"
    show_help
    exit 2
fi
defaults write com.apple.finder AppleShowAllFiles $yes_or_no
killall Finder