Re: [Bug-tar] [patch v3] Bug / question in tar

[Gene Heskett]

On Saturday 29 March 2014 16:49:10 Tim Kientzle did opine:

> On Mar 29, 2014, at 1:00 PM, Paul Eggert <address@hidden> wrote:
> > Tim Kientzle wrote:
> >> As long as it still reads the input files.
> > 
> > There is no need to read input files when the input data is not used
> > for anything.  People who want to fool tar into actually reading the
> > files can pipe its output to another program that discards it.
> 
> I'm curious.  If someone types the following command:
> 
>    tar cf /dev/null some files
> 
> What do you think they expect to happen?
> 
> I have heard of people using "tar cf /dev/null /mnt/cdrom" to test
> whether the files on a CD-ROM were readable.  If tar "optimizes" by not
> reading the files, that could lead a person relying on this behavior to
> erroneously believe the CD-ROM had no errors.
> 
> If you really believe that sending output to /dev/null should not do
> anything, make it a fatal error so people won't rely on it.
> 
> Tim

Thats a breakage killer too Tim.  I can think of at least one very mature 
backup program that does that just to get the estimate so it can diddle the 
schedule to try and even out the amount of tape used per backup session.  
Amanda TBE.

Cheers, Gene
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