Handy Command

ex.bash

#!/usr/bin/env bash

# Place this command to an arbitrary path e.g. bin/example.bash
# Grant a permission
#   chmod u+x bin/ex.bash
# Put a symlink without extension into top of project
#   ln -s bin/ex.bash ./ex
# Execute the command
#   ./ex init
# Use environment variable to pass arguments (Might better not to make the script such complicated) 
#   FOO_DIR="~/sample_path/" ./ex download

function ex() {
  set -u
  local SELF="$(basename $0)"
  local NAME="Example Command Desctiption"
  local UTIME="$(date +'%Y%m%d')"
  local WORK_DIR="$(pwd)"
  local PID_PATH="${WORK_DIR}/var/.pids"

  init() {
    echo "Do some initializations here"
  }

  __show-message() {
    echo "This method doesn't show up in usage if you put a prefix __ (double underscore)"
  }

  logs() {
    tail -F logs/*.log
  }

  download() {
    rsync -avzP --bwlimit=8000 example.com:/path/ ${FOO_DIR:=${WORK_DIR}}
  }

  usage() {
    echo -e "${SELF} -- ${NAME}\nUsage: ${SELF} [sub-command]\n[Sub-commands]:"
    declare -F | awk '{print "\t" $3}' | grep -v ${SELF} | grep -vE '^\t__[^_]+'
  }

  if [[ $# = 0 ]]; then
    usage
    echo "INFO: ${SELF} requires a sub-command"
  elif [[ "$(type -t $1)" = "function" ]]; then
    $1
  else
    usage
  fi
}

ex $1

Refer https://ymkjp.wordpress.com/2018/01/08/a-handy-command-to-put-into-your-project/ for more detail.