Bash Script using Flags and Options

#!/bin/bash

#:########################################################################
#: The option-string
#:
#: The option-string tells getopts which options to expect and which of them
#: must have an argument. The syntax is very simple . every option character
#: is simply named as is, this example-string would tell getopts to look
#: for -e, -d and -m:
#:
#: getopts fAx VARNAME
#:
#: When you want getopts to expect an argument for an option, just place
#: a : (colon) after the proper option flag. If you want -e to expect an
#: argument (i.e. to become -e ENVIRONMENT ) just do:
#:
#: getopts ed:m VARNAME
#:
#:########################################################################

function checkParam()
{

  # if no paramter was supplied, show usage
  text="Usage: $0 -e ENVIRONMENT -d DATE_FILENAME.TXT -m METRIC_FILENAME.TXT" 
  [ $# -eq 0 ] && { echo "$text"; exit 1; }

  # parse the flags and options
  while getopts "e:d:m:" opt; do
    case $opt in
      e)
        echo "-$opt $OPTARG $OPTIND $OPTERR was triggered!" >&2
        env=$OPTARG
        ;;
      d)
     echo "-$opt $OPTARG $OPTIND $OPTERR was triggered!" >&2
        fdate=$OPTARG
        ;;
      m)
     echo "-$opt $OPTARG $OPTIND $OPTERR was triggered!" >&2
        fmetric=$OPTARG
        ;;
      *)
        echo "Invalid option: -$opt $OPTARG $OPTIND $OPTERR" >&2
        ;;
    esac
  done

  # show the flags and options that were parsed
  echo "Environment: [$env]"
  echo "Date filename: [$fdate]"
  echo "Metric filename: [$fmetric]"

  # Check the given files exist #
  [ ! -f "$fdate" ] && { echo "Error: $fdate file not found."; exit 2; }
  [ ! -f "$fmetric" ] && { echo "Error: $fmetric file not found."; exit 2; }

  # Check the given files are not empty #
  [ ! -s "$fdate" ] && { echo "Error: $fdate file is empty."; exit 2; }
  [ ! -s "$fmetric" ] && { echo "Error: $fmetric file is empty."; exit 2; }
}

#: ## [ MAIN ] ###
checkParam $@