sdFileWrite(filename, contents)
sdFileAppend(filename, contents)
sdFileRead(filename, [offset, [length=256]])
sdFileSize(filename)

These functions provide a high-level access to the SD card file-system.

You can use sdFileWrite or sdFileAppend to create and replace or append a chunk of data on a file in the SD card.

The sdFileRead reads a string from the file (at most 256 bytes). If you want to read more data you can use the offset property to start reading from another location in the file.

The sdFileSize returns the file size in bytes.