args.sh

#!/bin/sh

error() {
  echo "foo: $1"
  exit 1
}

while [ $# -gt 0 ]; do
  case "$1" in
    -v)
      # option with value
      if [ -z "$2" ]; then
        error "option $1 expects a value"
      fi
      echo "$1: $2"
      shift
      ;;
    -o)
      # option without value
      echo "$1: true"
      ;;
    *)
      # non-option argument
      if [[ $1 == -* ]] ; then
        error "option $1 is invalid"
      fi
      echo "$1"
      ;;
  esac
  shift
done