Re: [Bug-tar] Tar cheats when directed to /dev/null

[Phillip Susi]

On 3/25/2010 1:14 PM, Sergey Poznyakoff wrote:
> Perhaps it was not worth spending a day: tar operates this way since
> v. 1.11 at least (i.e. since 1996, if my memory serves me), and it is
> documented in the tar manual (see "6.1 Choosing and Naming Archive
> Files"). In particular the docs explain one of the reasons tar operates
> this way:
> 
>    When the archive is being created to `/dev/null', GNU `tar' tries to
>    minimize input and output operations.  The Amanda backup system, when
>    used with GNU `tar', has an initial sizing pass which uses this
>    feature.

This is not mentioned in the man page and the info docs are not
distributed by default on debian based systems.  It doesn't really
matter how long it has been doing it for; wrong is wrong.  If you want a
size estimate then there should be a proper request for that, rather
than pretending to do a backup to null.