Default S4 root for Kit Kat using OSX?

Hi

Iv'e just updated to Kitkat 4.4 and now discovered I can no longer write to my sd card. There's an app I can use in the play store that will over come this but i need to be rooted. Are there any step by step instructions for rooting my S4 using Osx Lion, all seem to be for windows, can't find any anywhere?

TIA