How to parse arguments using getopts

echoback.sh

#!/bin/sh

# Uses getopts to parse passed arguments

# Show usage
show_help() {
  cat << EOF

  Usage: echoback -m message

  Echo back whatever is passed as message

  -h    display this help and exit
  -v    be verbose
  -m    string that should be echoed back

EOF
}

VERBOSE=0
OPTIND=1
while getopts "hvm:" opt; do
  case "$opt" in

  	# Show usage and exit
    h)
      show_help
      exit 0
      ;;

    # Verbose mode on
    v)
      VERBOSE=1
      echo 'Verbose mode is on'
      ;;

    # Echo the message back
    m)
      echo $OPTARG
      exit $?
      ;;
  esac
done

shift "$((OPTIND-1))"
show_help

Try

$ chmod +x echoback.sh
$ ./echoback.sh -h
$ ./echobash.sh -m "what goes around, comes around"