As I said, if it's too unbearable a hack for you to unlink() the file directly after creat()ing it (to get an anonymous file handle that nobody else can see), f

As I said, if it's too unbearable a hack for you to unlink() the file directly after creat()ing it (to get an anonymous file handle that nobody else can see), for the unlikely case that the system crashes just in between, then just go ahead and use O_TMPFILE. It was made for you! If you don't want to use O_TMPFILE (not super-portable) then just open(path, O_CREAT|O_EXCL). That fails should there be another file lying around, and you can try again with another random name. Btw. you can also just mmap(2) some anonymous non-disk-backed memory, and possibly open_memstream(3) on it to get a FILE * if that suits you better.