Parse Arguments in Bash in a convenient way

example.sh

#!/bin/bash -e

source parse-arguments.sh

REQUIRED_ARGUMENTS=(
  "arg-1"
  "arg-2"
)

OPTIONAL_ARGUMENTS=(
  "opt-1"
  "opt-2"
)

ARGUMENT_FLAGS=(
  "dry-run"
)

parseArguments --required=REQUIRED_ARGUMENTS --optional=OPTIONAL_ARGUMENTS --flags=ARGUMENT_FLAGS -- "$@"

# accessing defined arguments

echo "arg-1: $arg_1"
echo "arg-2: $arg_2"
echo "opt-1: $opt_1"
echo "opt-2: $opt_2"
echo "dry-run: $dry_run"

# accessing other arguments
echo "arguments: ${arguments[*]}"

# ./example.sh some --arg-1=foo other --arg-2=bar --opt-1=baz --dry-run arguments

###### output: ######

#  arg-1: foo
#  arg-2: bar
#  opt-1: baz
#  opt-2:
#  dry-run: true
#  arguments: some other arguments

parse-arguments.sh

#!/bin/bash -e

function convertBashVar() {
    echo "${1//-/_}"
}

function parseArguments() {
  # read the options
  OPTS=`getopt -o "" --longoptions required:,optional:,flags: -- "$@"`
  eval set -- "$OPTS"

  while true ; do
      case "$1" in
          --required)
            local -n REF_REQUIRED_ARGUMENTS=$2
            shift 2
          ;;
          --optional)
            local -n REF_OPTIONAL_ARGUMENTS=$2
            shift 2
          ;;
          --flags)
            local -n REF_ARGUMENT_FLAGS=$2
            shift 2
          ;;
          --)
            shift
            break
          ;;
          *)
            echo "Internal error!"
            exit 1
          ;;
      esac
  done

  LONG_OPTIONS=""
  if [ -n "${REF_OPTIONAL_ARGUMENTS}" ]; then
    LONG_OPTIONS+="$(printf "%s::," "${REF_OPTIONAL_ARGUMENTS[@]}")"
  fi
  if [ -n "${REF_REQUIRED_ARGUMENTS}" ]; then
    LONG_OPTIONS+="$(printf "%s:," "${REF_REQUIRED_ARGUMENTS[@]}")"
  fi
  if [ -n "${REF_ARGUMENT_FLAGS}" ]; then
    LONG_OPTIONS+="$(printf "%s," "${REF_ARGUMENT_FLAGS[@]}")"
  fi

  if [ -z "$LONG_OPTIONS" ]; then
    echo "No arguments provided"
    echo "Usage: $0 --required=REQUIRED_ARGUMENTS --optional=OPTIONAL_ARGUMENTS --flags=ARGUMENT_FLAGS -- \$@"
    exit 1
  fi

  # read arguments
  opts=$(getopt \
    --longoptions "$LONG_OPTIONS" \
    --name "$(basename "$0")" \
    --options "" \
    -- "$@"
  )

  eval set -- $opts

  for (( i = 1; i < $# + 1; )); do
    ArgName="${!i}"
    ArgName="${ArgName#--}"
    ValueIndex=$(($i + 1))
    Value="${!ValueIndex}"

    if [ -z "$ArgName" ]; then
      arguments=("${@:$(( $i + 1 ))}")
      break
    else
      if [[ " ${REF_OPTIONAL_ARGUMENTS[*]} " =~ " ${ArgName} " ]]; then
        declare -g "$(convertBashVar "$ArgName")=$Value"
        i=$(($i + 2))
      elif [[ " ${REF_REQUIRED_ARGUMENTS[*]} " =~ " ${ArgName} " ]]; then
        declare -g "$(convertBashVar "$ArgName")=$Value"
        i=$(($i + 2))
      elif [[ " ${REF_ARGUMENT_FLAGS[*]} " =~ " ${ArgName} " ]]; then
        declare -g "$(convertBashVar "$ArgName")=true"
        i=$(($i + 1))
      else
        echo "Error: Argument name '$ArgName' is not valid"
        exit 1
      fi
    fi
  done
}