The f_putc funciton puts a character to the file.
int f_putc ( int Chr, /* A character to put */ FIL* FileObject /* File object */ );
When the character was written successfuly, the function returns the character. When the function failed due to disk full or any error, an EOF will be returned.
The f_putc() is a wrapper function of f_write().
Available when _FS_READONLY == 0 and _USE_STRFUNC is 1 or 2. When it is set to 2, a '\n' is converted to "\r\n".