GNU bug report logs - #6268
Suggestion: truncate should allow -r and -s options together

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Message #26 received at 6268 <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Jim Meyering <jim <at> meyering.net>
Cc: 6268 <at> debbugs.gnu.org
Subject: Re: bug#6268: Suggestion: truncate should allow -r and -s options
	together
Date: Sat, 29 May 2010 01:03:08 +0100

[Message part 1 (text/plain, inline)]

On 28/05/10 14:17, Pádraig Brady wrote:
>> what about --ref=non-regular-file ?
>>
>> Perhaps truncate should refuse to use st_size info from
>> a non-regular file.
>>
>> Here's a pathological example:
>>
>>   $ echo abcdefgh > bar
>>   $ strace -e ftruncate ./truncate --ref=/dev/tty bar
>>   ftruncate(3, 0)                         = 0
>>   $ wc -c bar
>>   0 bar
>>
>> It's obvious that such an example is not likely in practice, but since
>> currently truncate's --ref uses stat, it would follow a symlink, too.
>>
>> For a directory you'd get unportable and probably surprising results.
>> Using such a reference size deserves at least a warning.
> 
> Yes that's safer. st_size is only defined for regular files
> (or shared mem), so I'll only allow regular files.
> I'll push a separate patch soon.
> 
> Since we're only referencing the size, there is the argument
> that we should be trying harder to get the size of block devices
> for example.  There are portability issues with that though,
> and doing outside of truncate is easy enough, so I'll leave that for now.

I actually removed all ignoring of errors for
non regular files, as well as not allowing
one to reference st_size for non regular files.

I'll push the attached tomorrow sometime.

cheers,
Pádraig.

[truncate-non-files.diff (text/x-patch, attachment)]

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