28 Jun
2024
28 Jun
'24
4:22 a.m.
On Jun 27, 2024, at 2:47 AM, Leah Neukirchen <leah(a)vuxu.org> wrote:
This feels more like a half done job. tar doesn't duplicate the data
so the extraction fails. cpio duplicates the data so fixing the bug
would be easy.
It is not at all clear what is the right choice (re whether to
duplicate the data or not), especially if I have a very large file
with multiple hard links. I tend to think *not* duplicating the
data is the right choice as you can always re-run tar x and extract
the original as well as the hard linked name. But you may think
differently.
In any case, the original culprit is libarchive (on FreeBSD) as Leah
pointed out, not OSX! What is more, dealing with hardlinks & copying
has always been troublesome.
ron minnich <rminnich(a)gmail.com> writes:
> ronsexcllentmbp:t rminnich$ cpio -ivt < ../t.cpio
> -rw-r--r-- 1 rminnich wheel 0 Jun 26 20:21 a
> -rw-r--r-- 2 rminnich wheel 0 Jun 26 20:21 b
> -rw-r--r-- 2 rminnich wheel 0 Jun 26 20:21 c link to b
>
> "c link to b"? wtf? Who thought that was a good idea? because ...
This is a bit tricky. Linux doesn't add ' link to b' so you
don't know what c is linked to. If you want to show this info
using any printable char, you get in trouble as a file of the
same name can be made!
Tar is a bit better:
$ touch a; ln a b; touch 'b link to a'; ln 'b link to a' c
$ ls | tar -cI - | tar -tv
-rw-r--r-- 0 bakul wheel 58 Jun 27 14:50 a
hrw-r--r-- 0 bakul wheel 0 Jun 27 14:50 b link to a
-rw-r--r-- 0 bakul wheel 0 Jun 27 14:39 b link to a
hrw-r--r-- 0 bakul wheel 0 Jun 27 14:39 c link to b link to a
That 'h' in this first column tells you this is a hard link. Not so
with cpio!
$ ls | cpio -o | cpio -ivt
2 blocks
-rw-r--r-- 2 bakul wheel 58 Jun 27 14:50 a
-rw-r--r-- 2 bakul wheel 58 Jun 27 14:50 b link to a
-rw-r--r-- 2 bakul wheel 0 Jun 27 14:39 b link to a
-rw-r--r-- 2 bakul wheel 0 Jun 27 14:39 c link to b link to a
I think at the very least this extra info should be displayed
using another flag.
ronsexcllentmbp:t rminnich$ touch 'c link to b'
ronsexcllentmbp:t rminnich$ ls -l
total 0
-rw-r--r-- 1 rminnich wheel 0 Jun 26 20:21 a
-rw-r--r-- 2 rminnich wheel 0 Jun 26 20:21 b
-rw-r--r-- 2 rminnich wheel 0 Jun 26 20:21 c
-rw-r--r-- 1 rminnich wheel 0 Jun 26 20:22 c link to b
This is a feature of libarchive (cpio since FreeBSD 8), note that
without -v it prints the actual names as tools expect it.
(Similarly, symlinks are printed as "c -> b".)
More fun is that it's not able to extract only "c", even tho the ASCII
cpio format stores hard links by duplicating the data...