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

[Sergey Poznyakoff]

Phillip Susi <address@hidden> ha escrit:

> After spending a day going out of my mind trying to figure out very
> strange results from some performance comparisons I was doing, I finally
> figured out that tar was cheating.

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.

Regards,
Sergey