#!/bin/bash

filename=
interface=

function usage() {
    echo $0 -i interface -f filename
    exit 1
}

function extract_params() {

  if [ $# -ne 4 ]
  then
      usage
  fi

  while [ $# -gt 1 ]
  do
      case $1 in
        -f)
            filename=$2
            ;;
        -i)
            interface=$2
            ;;
        *)
            usage
            ;;
    esac
    shift
    shift
done

}

extract_params $@