how can I delete contents of an SD card in arduino?

Question

I have a datafile, datalog.txt I can open, read and write cool. What is the best way to delete all the file contents? Should I try rewriting the SD card file with NULL data? I have been reading the "SD.h" header file. I see a flush() and truncate() function should I use one of these?

or maybe I should just close and reopen the file, and overwrite the data. But I'm concerned that this might lead to some miss representations if the old data is not completely removed.

I am using a teensy 4.1 with built_in SD card.

Answer 1

To remove a file use SD.remove("datalog.txt");

SD library's FILE_WRITE is O_READ | O_WRITE | O_CREAT | O_APPEND so it would append at the end of the existing file.

to start with an empty file: File file = FS.open("datalog.txt", O_READ | O_WRITE | O_CREAT);

EDIT: opening the file with O_READ | O_WRITE | O_CREAT doesn't clear the content of the file, only starts to overwrite it from the beginning.