How to check if a file of given length can be created?

Question

I want to create a non-sparse file of a given length (i.e. 2GB), but I want to check if that is possible before actually writing stuff to disk.

In other words I want to avoid getting ENOSPC (No space left on device) while writing. I'd prefer not to create a "test file" of size 2GB or things like that just to check that there is enough space left.

Is that possible?

Answer 1

Use posix_fallocate(3).

From the description:

The function posix_fallocate() ensures that disk space is allocated for the file referred to by the descriptor fd for the bytes in the range starting at offset and continuing for len bytes. After a successful call to posix_fallocate(), subsequent writes to bytes in the specified range are guaranteed not to fail because of lack of disk space