An Implementation of the Arduino/Sparkfun SD Card Library for the Spark Core
This might be tricky to build online due to the number of files required. I have not tried to set it up online. Using the Spark-CLI tool might be a better way to build it online.
If you are building locally, place the files here:
// put the entire 'libraries' folder and everything in it here
..\core-firmware\libraries
// rename one of the example apps located at ..\libraries\sd\examples\
// to application.cpp and place it here
..\core-firmware\src\application.cpp
Thanks to @choosatron for your work on this!