Re: [Zutils-bug] zcat: misses -t option

[Antonio Diaz Diaz]

Hi Daniel,

Daniel Baumann wrote:
> I recently got the following bug-report in Debian, where there's a
> problem that zcat from zutils doesn't implement the -t option:
>
>    https://bugs.debian.org/903931
>
> Do you think, such an option could be added to zutils?

But the zcat from zutils does implement the -t option[1].

[1] http://www.nongnu.org/zutils/manual/zutils_manual.html#Zcat

It seems that there are two ways of implementing *zcat programs out 
there. The zcat from zutils is a complete implementation of a cat 
program like the one from GNU coreutils[2] but with transparent 
decompression. I have invested a lot of work to make it work well.

[2] 
http://www.gnu.org/software/coreutils/manual/html_node/cat-invocation.html#cat-invocation

The rest of the *zcat programs out there seem to be just wrapper 
scripts. The zcat from gzip boils down to 'exec gzip -cd "$@"'.

The problem, IMO, is in the xcpio() function of unmkinitramfs. It should 
use 'gzip -t' instead of 'zcat -t', just as it already uses 'bzip2 -t' 
and 'lzop -t'. Think that posix zcat does not document a -t option[3] 
and therefore 'zcat -t' is not a portable way to check file integrity.

[3] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/zcat.html


Best regards,
Antonio.