On Sat, Nov 27, 2021 at 11:03 AM Brian Candler <b.cand...@pobox.com> wrote:
> Whether (1) or (2) applies depends whether the final return is a "naked" > one or not. In this case it isn't: > > > *return io.Copy(dst, src)* > > Therefore, the value returned is whatever io.Copy() returns > That is not true <https://go.dev/play/p/NlnCjMA3n3O>. FWIW I think the code in the blog post is bad, as it doesn't check the errors from `Close`. But a) it's an old post, I don't know if it's worth fixing it and b) fixing it might distort the point - teaching the mechanics of defer. The best way to fix it would probably be to do `return written, dst.Close()` - i.e. call `Close()` twice. > There is a wider question as to whether you should check the error return > from Close() in the first place. In some rare cases it *might* show > something, e.g. Close() when you are *writing* a file may return disk full > errors for some filesystems. However it doesn't give a guarantee that all > errors are caught. > > If you need to guarantee that the data was successfully written to disk > then you should call Fsync() and check the return value of that, but that's > an expensive operation (it forces the OS to write dirty buffers to disk). > Even then there are issues to beware of, especially if multiple threads are > calling Fsync() on the same file. See > https://www.youtube.com/watch?v=74c19hwY2oE > https://wiki.postgresql.org/wiki/Fsync_Errors > # both linked from: https://docs.ceph.com/en/mimic/cephfs/posix/ > > Most applications don't need this type of guarantee, i.e. if the disk > becomes full or there are I/O errors then they accept that the data on disk > will be corrupt. > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/774265d3-f574-4bf7-bef7-ece3cd79643bn%40googlegroups.com > <https://groups.google.com/d/msgid/golang-nuts/774265d3-f574-4bf7-bef7-ece3cd79643bn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAEkBMfE2Tm26h0VOb1L03%3DenG1vnbVB0qeSZKaC1vjR3ZvohyA%40mail.gmail.com.
