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--directory option etc in GNU tar (1.12)
From: |
Kim Lester |
Subject: |
--directory option etc in GNU tar (1.12) |
Date: |
Fri, 11 Oct 2002 01:06:04 +1000 |
Hi,
The -C (--directory) option is only defined (apparently) for creation
(and it requires a filename after it)
I'm not sure of the elegant way to force tar to extract
TO a specific dir root/base.
Of course I can type: cd /frodo; tar -xvf tarfile
but this requires me to provide an absolute path to tarfile.
It seems reasonable at first glance to want:
tar -xvf tarfile --directory=/frodo
and have tar chdir() just before it starts work.
This has benefits when calling tar from scripts etc as it
doesn't chantge the current dir and makes locating the tarfile
simpler.
Would appreciate feedback if you have time.
It's late so I may be missing something blindingly obvious.
Also whilst I think of it some constructive feedback
1) I think gnu tar requires a few too many options to get a perfect
copy incluiding times, perms etc. And I forget if it handles all
times well (c,m and a).
IMHO the following options could be made available
in a single letter option (yeah I know horrible but
pragmatic:
--same-owner --atime-preserve
--preserve-permission --preserve-order
(--preserve seems to go half way)
cpio -dump ... makes a near perfect copy.
2) I would like to create (gzipped) tar archives from a program.
Perhaps I'm weird but I want to use .tgz as an interchange
format
for a packaging system I have. At the simplest level I could
creat the files individually on disk but I need to be able to
specify their uid/gid/perms/location explicitly via API since
they would be untarred in a different directory structure
to the one they are packed from.
This may sound silly but when you realise it is a package
installation program it makes sense.
If any has the time to let me know if this is likely
to be easy using libtar.a or "horrendously difficult because
tar funcs just don't work that way" I'd appreciate it.
3) The docs may be unclear on what happens to dir perms
if untarring and the dir already exists. Does tar only
set dir perms if it has to create the dir?
ie if the directory exists does tar apply perms from the tar
file?
4) I think --recursive-unlink is probably evil and should
be removed on the principle that it affects files
which have nothing to do with the tar archive.
Presumably if one wants a clean untar one can do
an 'rm -fr' and one then is aware of the action.
regards
kim
p.s. Happy to consider making any suggested changes myself if I
get the chance after your feedback. No promises though
free time is a rare beast.
Kim Lester,
Senior Engineer,
Datafusion and Visualisation Systems
www.dfusion.com.au
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