OK, let me show you nice part about ruby. It is really very expressive and allow you easy express idea how it work.
In human language you want find device that exists and doesn't have vlan config...so if I write it I try to follow my mind this way:
```
def FcoeOnInterface?(device, vlans) 
  return false unless FileUtils.Exists("/etc/fcoe/cfg-#{device}")

  # no ifcfg-<if>.<vlan> written for vlan = 0 (see WriteSysconfigFiles() ) 
  vlans.none? do |vlan_cfg|
    FileUtils.Exists  "/etc/sysconfig/network/ifcfg-#{device}.#{vlan_cfg["vlan"]}"
  end
end
```

if you have any question about code above, feel free to ask.