bash-arg-passing-1.sh

#!/usr/bin/env bash

# Set some default values:
ALPHA=a
BETA=b
CHARLIE=c
DELTA=d

usage() {
  echo "Usage: alphabet [ -a | --alpha ] [ -b | --beta ]
                        [ -c | --charlie CHARLIE ]
                        [ -d | --delta   DELTA   ] filename(s)"
  exit 2
}

PARSED_ARGUMENTS=$(getopt -a -n alphabet -o abc:d: --long alpha,bravo,charlie:,delta: -- "$@")
VALID_ARGUMENTS=$?
if [ "$VALID_ARGUMENTS" != "0" ]; then
  usage
fi

echo "PARSED_ARGUMENTS is $PARSED_ARGUMENTS"
eval set -- "$PARSED_ARGUMENTS"
while :; do
  case "$1" in
  -a | --alpha)
    ALPHA=1
    shift
    ;;
  -b | --beta)
    BETA=1
    shift
    ;;
  -c | --charlie)
    CHARLIE="$2"
    shift 2
    ;;
  -d | --delta)
    DELTA="$2"
    shift 2
    ;;
  # -- means the end of the arguments; drop this, and break out of the while loop
  --)
    shift
    break
    ;;
  # If invalid options were passed, then getopt should have reported an error,
  # which we checked as VALID_ARGUMENTS when getopt was called...
  *)
    echo "Unexpected option: $1 - this should not happen."
    usage
    ;;
  esac
done

echo "ALPHA   : $ALPHA"
echo "BETA    : $BETA "
echo "CHARLIE : $CHARLIE"
echo "DELTA   : $DELTA"
echo "Parameters remaining are: $*"