Re: inotify back end for tail -f on linux

[Pádraig Brady]

Jim Meyering wrote:

> diff --git a/NEWS b/NEWS
> index d7695e4..754f9e2 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -28,6 +28,8 @@ GNU coreutils NEWS                                    -*- 
> outline -*-
>    sort accepts a new option, --human-numeric-sort (-h): sort numbers
>    while honoring human readable suffixes like KiB and MB etc.
> 
> +  tail uses inotify when possible.
> +
> 

That's a little terse. How about:

tail --follow uses inotify when possible to be more responsive
to file changes and also be more scalable when many files are monitored.

> diff --git a/src/tail.c b/src/tail.c
> index 9d416e1..059ee82 100644
> --- a/src/tail.c
> +++ b/src/tail.c
> @@ -1691,7 +1933,24 @@ main (int argc, char **argv)
>      ok &= tail_file (&F[i], n_units);
> 
>    if (forever)
> -    tail_forever (F, n_files, sleep_interval);
> +    {
> +#if HAVE_INOTIFY
> +      if (pid == 0)
> +        {
> +          int wd = inotify_init ();
> +          if (wd < 0)
> +            error (0, errno, _("inotify cannot be used, reverting to 
> polling"));

Do we need to warn here since the fallback is functionally equivalent?
It's OK if the error is rare, but I'm worried that errors might be issued
from /sys or /proc or if the user boots an old kernel, or whatever.
Well not that worried TBH, just mentioning it :)

cheers,
Pádraig.