Save data only on the Spresense main board

I found the following code in camera_main.c

/*In SD card is available, use SD card.
 * Otherwise, use SPI flash.
 */

ret = stat("/mnt/sd0", & stat_buf);
if(ret<0)
  {
    save_dir="/mnt/spif";
  }
else
  {
    save_dir="/mnt/sd0";
  }

As a trial, I created the file below /mnt/spif, but it didn't disappear even when I turned it off/on, so I think it's probably okay.

I am in charge of SPRESENSE support for Sony.
I would like to reply to your inquiry.

As you have already checked, /mnt/spif has been allocated Flash space.
For example, you can access the file "hoge.txt" with the pathname "/mnt/spif/hoge.txt".
You can use C-language standard functions such as fopen, fwrite, fread, and fclose.

Here are some simple examples of the program:

# include 

FILE*fp;

fp = fopen("/mnt/spif/hoge.txt", "w");
fwrite(buf,size,n,fp);// Write
fclose(fp);

fp = fopen("/mnt/spif/hoge.txt", "r");
fread(buf,size,n,fp); // Read
fclose(fp);

Thank you for your continued support for the Presense.