Bash script to run functions using arguments

script.sh

# Documentation
display_help() {
    echo "Usage: [variable=value] $0" >&2
    echo
    echo "   -m, --my_function          run my_function"
    echo "   -h, --help                 display help"
    echo
    # echo some stuff here for the -a or --add-options
    exit 1
}

default_function() {
  VAR = "var"
}

my_function() {
  default_function
  echo ${VAR}
}

# Available options
while :
do
    case "$1" in
      -h | --help)
          display_help  # Call help function
          exit 0
          ;;

      -m | --my_function)
          my_function  # Call custom function
          break
          ;;

      "")
          default_function  # Call default function
          break
          ;;

      --) # End of all options
          shift
          break
          ;;
      -*)
          echo "Error: Unknown option: $1" >&2
          ## or call function display_help
          exit 1
          ;;
          
      *)  # No more options
          break
          ;;
    esac
done