Bash getopts - normalize flags

normalize_flags.sh

#!/usr/bin/env bash

# Normalize --long-flags to -s short ones for use with getopts.
normalize_flags() {
  local shortopt longopt
  local -a args=()
  local -A spec=()

  # Process option definitions until we hit the -- separator
  while [[ "$#" -gt 0 && "$1" != -- ]]; do
    # Split the "short/long" option spec and save the mapping
    shortopt="${1%%/*}"
    longopt="${1#*/}"
    spec["--${longopt}"]="-${shortopt}"
    shift
  done

  # Check for the required -- separator
  if [[ "$1" != -- ]]; then
    printf >&2 'normalize_args: %s\n' "Missing required -- separator"
    return 1
  fi
  shift # Skip the -- separator

  # Handle longopt to shortopt conversion,
  # respecting anything after an optional --
  while [[ "$#" -gt 0 ]]; do
    if [[ -n "${spec["$1"]}" ]]; then
      args+=("${spec["$1"]}")
    elif [[ "$1" == -- ]]; then
      args+=("$@")
      break
    else
      args+=("$1")
    fi
    shift
  done

  # Return new args via the reply array
  typeset -ga reply=("${args[@]}")
}

usage.sh

### Usage

# call normalize_flags defining -s short to --long option mappings where appropriate
normalize_flags 'a/any' 'd/do-something' 'h/help' 'v/version' 'x/extra' -- "$@"
set -- "${reply[@]}"
unset reply

# Use getopts confidently, now that all options are short
while getopts ":adhvx:" opt; do
  case "$opt" in
    a) echo "Option A" ;;
    h) echo "Help" ;;
    d) echo "Option D" ;;
    v) echo "Version" ;;
    z) echo "Extra: $OPTARG" ;;
    \?) echo "Invalid option"; return 1 ;;
  esac
done

# Ensure OPTIND is at least 1 before shifting
[[ $OPTIND -gt 1 ]] && shift $((OPTIND - 1))
unset OPTARG OPTIND OPTOPT