Re: [PATCH] shred: provide --remove methods to avoid excessive syncing

[Bernhard Voelker]

On 11/20/2013 01:45 AM, Pádraig Brady wrote:
> Before I merge this I'd like to understand fully
> the reason why shred currently defaults to writing
> out progressively shorter names. From the source..
> 
> /* Repeatedly rename a file with shorter and shorter names,
>    to obliterate all traces of the file name on any system that
>    adds a trailing delimiter to on-disk file names and reuses
>    the same directory slot.  */

That sounds like the filesystem terminates the file name on disk,
e.g. with a NUL character, i.e. during each rename() the last
character gets overwritten so that all characters in the original
name are changed to the terminating character:

  's',  'e',  'c',  'r',  'e',  't', '\0'
  's',  'e',  'c',  'r',  'e', '\0', '\0'
  's',  'e',  'c',  'r', '\0', '\0', '\0'
  's',  'e',  'c', '\0', '\0', '\0', '\0'
  's',  'e', '\0', '\0', '\0', '\0', '\0'
  's', '\0', '\0', '\0', '\0', '\0', '\0'

(Just a guess, of course.)

Have a nice day,
Berny