gistfile1.sh

cp_dmg() {
    dmg="$1"
    file="$2"
    destination="$3"
    mountpoint=$(hdiutil attach "$dmg" -nobrowse -plist|xpath '//key[.="mount-point"]/following-sibling::*[1]' 2> /dev/null|sed -e 's/<\/*string>//g')
    cp "${mountpoint}/$file" "$destination"
    hdiutil detach -quiet "$mountpoint"
}