Roholt

Whenever writing a script you might want to enable some options depending on what you provide on the CLI.

I’ve created a bash script template to getting started quick with a bash script. You can specify full options or the short ones with arguments or without.

#!/bin/bash
# Version 2.0
# Script template

set -eou pipefail

DO_OPT_A=false
DO_OPT_B=false

# directory of the script, can be useful for locating files which are next to the script.
THISDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"

function main() {
  check_root

  do_parse_opts $@

  [[ ${DO_OPT_A}   = true ]] && check_opt_a_prerequisites
  [[ ${DO_OPT_B}   = true ]] && check_opt_b_prerequisites

  print_info "Checks OK, you have 2s to abort now!"
  sleep 2
  echo ""

  [[ ${DO_OPT_A} = true ]] && {
    do_opt_a_function
  }

  [[ ${DO_OPT_B} = true ]] && {
    do_opt_b_function
  }
}

function show_help() {
  echo "Scripting template :)"

  echo "Usage:"
  echo "    $0 [-a/--option_a] [-b/--option_b <arg>]"

  echo "        *  [-h/--help]      Print this help"
  echo "        *  [-a/--option_a]  Perform option A"
  echo "        *  [-b/--option_b <arg>]  Perform option B with argument"
  echo ""
  exit 1
}

function do_parse_opts() {
  # convert long options to shorts
  for arg in "$@"; do
    shift
    case "$arg" in
        "--help")       set -- "$@" "-h" ;;
        "--option_a")   set -- "$@" "-a" ;;
        "--option_b")   set -- "$@" "-b" ;;
        *)              set -- "$@" "$arg"
    esac
  done

  OPTIND=1 # Reset in case getopts has been used previously in the shell.
  while getopts "hab:" opt; do
      case "$opt" in
      h)
          show_help
          exit 0
          ;;
      a)  DO_OPT_A=true
          ;;
      b)  DO_OPT_B=true
          BARG=$OPTARG
          ;;
      esac
  done

  shift $((OPTIND-1))

  [ "${1:-}" = "--" ] && shift

  print_info "DO_OPT_A    = $DO_OPT_A"
  print_info "DO_OPT_B    = $DO_OPT_B"

  [[ ${DO_OPT_A} = false ]] && [[ ${DO_OPT_B} = false ]] && {
    print_info "Hey! Your provided no options, this might help:"
    echo ""
    show_help
  }

  echo ""
}

function check_root() {
    [[ $EUID -ne 0 ]] && {
        echo "[ERROR]     This script must be run as root"
        show_help
    }
}

function check_opt_a_prerequisites() {
    print_info "Checking option A prerequisites"
    sleep 1
    print_ok
}

function check_opt_b_prerequisites() {
    print_info "Checking option B prerequisites"
    sleep 1
    print_ok
}


function do_opt_a_function() {
    print_info "Performing A"
    sleep 1
    print_ok
}


function do_opt_b_function() {
    print_info "Performing B, with arg: ${BARG}"
    sleep 1
    print_ok
}


function print_ok() {
  echo "[OK]"
}

function print_info() {
  echo "[INFO]      $1..."
}

function print_error() {
  echo "[ERROR]     $1"
  exit 1
}


main $@

print_info "All done!"
echo "[OK]"