I always wondered how scripts passed variables beginning with a '-', i.e 'foo.sh -q', or 'tar -zxfv' and so on.

I knew that '$1' in bash takes the first extra variable sent at the shell, but that can be any sort of word, not specifically a '-' parameter. Does that make sense?

Anyway, it turns out you can use this neat getopts function like so, with a case statement. This way you can also output a 'usage' mini-manual when a variable that is unrecognised, is passed:

usage()
{
cat << EOF
usage: $0 -option
 
Use this script to rsync this to that :)
 
OPTIONS:
   -v      Be verbose, see what is transferring
   -q      Be quiet, hide transfer info except errors
EOF
}
 
while getopts ":vq" optname
  do
    case $optname in
      v)
        rsync -aHPv /path/to/dir remote:/path/to/
        ;;
      q)
        rsync -aHPq /path/to/dir remote:/path/to/
        ;;
      ?)
        usage
        exit
        ;;
    esac
  done

The ':' at the start of the getopts string sets '?' as parameter if it is unrecognised. You then use '?)' in the case statement to catch these erroneous paramaters (if I've understood all this correctly)

A much more concise explanation is offered here.