If you want to delete the content of an existing file just open it with the additional mode 'O_TRUNC'.
The code might look like this:
myFile = SD.open("filename", FILE_WRITE | O_TRUNC);
A complete list of all modes is here:
- FILE_READ: open the file for reading, starting at the beginning of the file.
- FILE_WRITE: open the file for reading and writing, starting at the end of the file.
- O_READ: open the file for reading, starting at the beginning of the file.
- O_RDONLY: same as O_READ.
- O_WRITE: open() file for writing, starting at the beginning of the file.
- O_WRONLY: same as O_WRITE
- O_RDWR: is a compination of (O_READ | O_WRITE)
- O_ACCMODE: is a combination of (O_READ | O_WRITE)
- O_APPEND: makes only sense with O_WRITE. Writing will be continued at the and end of the file
- O_SYNC: call sync() after each write
- O_CREAT: create the file if nonexistent */
- O_EXCL: If O_CREAT and O_EXCL are set, open() shall fail if the file exists
- O_TRUNC: truncate the file to zero length
Might be helpful
Heinz 