[Bug-tar] Return value for "file changed as we read it"

[Richard Thomas]

Hi, I had a look in the archive to see if this had been covered already 
but didn't find anything.

I just installed a new Debian server, the version of tar is 1.16 where 
before it has been 1.14. My backup script is now failing where 
previously it had functioned fine. It appears that tar is returning 1 
when a file changes when being read (I have verified this by tarring the 
output of tar). I found the below email which indicates that it should 
not be a problems (see at bottom of post). But when I run the example, 
it too returns 1. Is this a functional change for tar? Is there a way to 
compensate for it? We use it on servers where files are changing constantly.

I have to say that I am impressed with the progress in tar (the improved 
--exlude is much better) but am a little concerned at how 
backwards-compatibility is being maintained.

Thanks

Rich

   DNS2Svr:~# COUNT=100000
   DNS2Svr:~# dd if=/dev/zero of=file count=$COUNT
   100000+0 records in
   100000+0 records out
   51200000 bytes (51 MB) copied, 1.30391 seconds, 39.3 MB/s
   DNS2Svr:~# dd if=/dev/zero of=file count=$COUNT seek=$COUNT &
   [1] 2467
   DNS2Svr:~# tar cf archive file
   tar: file: file changed as we read it
   DNS2Svr:~# echo $?100000+0 records in
   100000+0 records out
   51200000 bytes (51 MB) copied, 2.89545 seconds, 17.7 MB/s

   1


>   Re: [Bug-tar] Separate return code when file changes while being read
>
> Sergey Poznyakoff
> Sat, 14 Oct 2006 04:14:14 -0700
>
> Steve Bergman <[EMAIL PROTECTED]> wrote:
>
> > If a file changes while tar is reading it, tar returns the same code as
> > when there is a major problem like a tape write error.
> > 
> > This makes it unusable for automated nightly backups.  It is perfectly
> > reasonable to want to include, for example, log files in the backup,
> > which might be appended to while being read.
>
> If the file is appended, tar exits with zero exit code. Try this test:
>
> COUNT=100000
> dd if=/dev/zero of=file count=$COUNT 
> dd if=/dev/zero of=file count=$COUNT seek=$COUNT &
> tar cf archive file
> echo $?
>
> It gives:
>
> tar: file: file changed as we read it
> 0
>
> However, if the file is trucated, tar exits with status 2, indeed.
>
> > Certainly, it is reasonable to return a nonzero code in the case that a
> > file changes while being read, but it should not be the *same* nonzero
> > code as for more serious problems.
>
> Yes, I agree with that.
>
> Regards,
> Sergey