Re: [PATCH] tail should dereference watched file

[Pádraig Brady]

On 09/13/2013 04:42 PM, Ondrej Oprala wrote:
> Hi,
> 
> Since inotify is dereferencing the files it's told to watch (according to 
> flags tail sets), the watched files should be dereferenced outside the 
> inotify_* family of functions as well.
> Example:
> $ echo 1  > file
> $ ln -sf file{,-link}
> $ tail -F ./file-link > out 2>/dev/null &
> $ rm file
> $ echo 2 > file
> $ kill %1
> $ cat out
> results: out only contains the contents of "file" before it was deleted.
> expected results: tail picks up on "file"'s reappearance.
> 
> To be precise, tail actually picks up on it. However, the list of watched 
> files from inotify is a list of files after dereferencing, whereas tail 
> compares it to the filenames of symlinks it got as arguments, resulting ofc 
> in unhappy users.
> Thanks,
> Ondrej

Yes this regression is inotify specific
as this does the right thing (through implicit dereferencing)

  tail ---disable-inotify -s.1 -F ./file-link

So you changed:

> +  for (i = 0; i < n_files; i++) {
> +    if (!lstat(file[i], &st) && S_ISLNK(st.st_mode))
> +        F[i].name = xreadlink(file[i]);

Does this cater for links to files in different directories too?
I'll do some more testing later.

thanks!
Pádraig.