Re: mmotm 2019-07-04-15-01 uploaded (gpu/drm/i915/oa/)

[Joe Perches]

On Thu, 2019-07-04 at 22:09 -0700, Andrew Morton wrote:
> diff(1) doesn't seem to know how to handle a zero-length file.
> 
> y:/home/akpm> mkdir foo
> y:/home/akpm> cd foo
> y:/home/akpm/foo> touch x
> y:/home/akpm/foo> diff -uN x y
> y:/home/akpm/foo> date > x
> y:/home/akpm/foo> diff -uN x y
> --- x   2019-07-04 21:58:37.815028211 -0700
> +++ y   1969-12-31 16:00:00.000000000 -0800
> @@ -1 +0,0 @@
> -Thu Jul  4 21:58:37 PDT 2019
> 
> So when comparing a zero-length file with a non-existent file, diff
> produces no output.

Why use the -N option ?

$ diff --help
[...]
  -N, --new-file                  treat absent files as empty

otherwise

$ cd $(mktemp -d -p .)
$ touch x
$ diff -u x y
diff: y: No such file or directory