source: trunk/essentials/app-shells/bash/examples/functions/sort-pos-params

# Sort the positional paramters.
# Make sure the positional parameters are passed as arguments to the function.
# If -u is the first arg, remove duplicate array members.
sort_posparams()
{
        local -a R
        local u

        case "$1" in
        -u)     u=-u ; shift ;;
        esac

        # if you want the case of no positional parameters to return success,
        # remove the error message and return 0
        if [ $# -eq 0 ]; then
                echo "$FUNCNAME: argument expected" >&2
                return 1
        fi

        # make R a copy of the positional parameters
        R=( "${@}" )

        # sort R.
        R=( $( printf "%s\n" "${R[@]}" | sort $u) )

        printf "%s\n" "${R[@]}"
        return 0
}

# will print everything on separate lines
set -- 3 1 4 1 5 9 2 6 5 3 2
sort_posparams "$@"

# sets without preserving quoted parameters
set -- $( sort_posparams "$@" )
echo "$@"
echo $#

# sets preserving quoted parameters, beware pos params with embedded newlines
set -- 'a b' 'a c' 'x z'

oifs=$IFS
IFS=$'\n'
set -- $( sort_posparams "$@" )
IFS="$oifs"

echo "$@"
echo $#

sort_posparams