I think a more “standard” and certainly portable way to do this is with a tmp
file, and a rename/move at the end - along with a clean-up of tmp at
application start (if worried about crashes).
Using the proper file and process permissions on the tmp file - since you need
these to protect the final file anyway.
> On Oct 12, 2018, at 12:21 AM, Sam Whited <s...@samwhited.com> wrote:
>
> On Thu, Oct 11, 2018, at 18:48, Greg Saylor wrote:
>> 1. Create a temporary file and squirrel away the file handle
>> 2. Unlink the temporary file by name
>> 3. Various functions would write stuff to the file
>> 4. If the programs completes to some successful state, create a hardlink to
>> the file handle with the final filename
>
> The golang.org/x/sys/unix [1] package gives you a lower level interface that
> might be familiar to you if you're used to using C. Something like this is
> probably similar to what you were doing (though you'll need /proc mounted,
> I'm not sure if there's a better way to do that):
>
> oldfd, err := unix.Open(".", unix.O_TMPFILE|unix.O_RDWR,
> unix.S_IRUSR|unix.S_IWUSR)
> if err != nil {
> panic(err)
> }
>
> f := os.NewFile(uintptr(oldfd), "myoldfile")
> _, err = f.Write([]byte("Hello, World"))
> if err != nil {
> panic(err)
> }
>
> dir, err := os.Open(".")
> if err != nil {
> panic(err)
> }
> procdir, err := os.Open("/proc/self/fd/")
> if err != nil {
> panic(err)
> }
>
> err = unix.Linkat(int(procdir.Fd()), strconv.Itoa(oldfd),
> int(dir.Fd()), "mynewfile", unix.AT_SYMLINK_FOLLOW)
> if err != nil {
> panic(err)
> }
>
> —Sam
>
> [1]: https://godoc.org/golang.org/x/sys/unix
>
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