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unpacking .z files

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  unpacking .z files sblinkhorn <steve@prd.co.uk> - 2011-07-19 05:02 -0700
    Re: unpacking .z files Mark Adler <madler@alumni.caltech.edu> - 2011-07-19 23:33 -0700
      Re: unpacking .z files sblinkhorn <steve@prd.co.uk> - 2011-07-20 04:11 -0700
        Re: unpacking .z files glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2011-07-20 16:39 +0000
        Re: unpacking .z files Mark Adler <madler@alumni.caltech.edu> - 2011-07-22 22:09 -0700
          Re: unpacking .z files sblinkhorn <steve@prd.co.uk> - 2011-07-28 11:15 -0700
          Re: unpacking .z files sblinkhorn <steve@prd.co.uk> - 2011-07-29 02:53 -0700
            Re: unpacking .z files Mark Adler <madler@alumni.caltech.edu> - 2011-07-29 08:21 -0700
            Re: unpacking .z files Mark Adler <madler@alumni.caltech.edu> - 2011-07-31 08:21 -0700

#429 — unpacking .z files

I have an archive of files originally created on an NCR Tower running
a version 7 Unix derivative, all compressed using the pack utility and
having a .z extension.   According to the documentation, GNU gunzip
ought to be able to unpack these files, but despite there being code
in the sources that looks appropriate, it doesn't.   The files are not
corrupted because if I take them one at a time onto a DOS box,
pcat.exe from my old MKS toolkit does read them.

I want to have the possibility of systematically unpacking all of them
on the NetBSD servers where they currently live.

Advice please?

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#431

On 2011-07-19 05:02:46 -0700, sblinkhorn said:
> According to the documentation, GNU gunzip ought to be able to unpack 
> these files, but despite there being code in the sources that looks 
> appropriate, it doesn't.

What happens when you try?  What are the first two bytes of an example .z file?

Mark

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#433

On Jul 20, 7:33 am, Mark Adler <mad...@alumni.caltech.edu> wrote:
> On 2011-07-19 05:02:46 -0700, sblinkhorn said:
>
> > According to the documentation, GNU gunzip ought to be able to unpack
> > these files, but despite there being code in the sources that looks
> > appropriate, it doesn't.
>
> What happens when you try?  What are the first two bytes of an example .z file?
>

Thanks for picking this up.

The error message is, e.g. :

 gzip: bn1out.z: not in gzip format

od -c reports, e.g.:

0001540  226 262   |   h   s   r   n 261   h   c   # 031   _  \r 367
Z
0001560    d 207 307 364   i   a 271 305 300 210 370 030 361   $ 024
225
0001600  006     313   L   e   J   C 346 240 020     202 270 342
\0   !

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#444

sblinkhorn <steve@prd.co.uk> wrote:
> On Jul 20, 7:33 am, Mark Adler <mad...@alumni.caltech.edu> wrote:

(snip)
>> What happens when you try?  What are the first two 
>> bytes of an example .z file?


> Thanks for picking this up.

> The error message is, e.g. :

> gzip: bn1out.z: not in gzip format

> od -c reports, e.g.:

> 0001540  226 262   |   h   s   r   n 261   h   c   # 031   _  \r 367
> Z
> 0001560    d 207 307 364   i   a 271 305 300 210 370 030 361   $ 024
> 225
> 0001600  006     313   L   e   J   C 346 240 020     202 270 342
> \0   !

What is od -c (or od -x) output of the first bytes?  

Also, use the file command which usually identifies the magic
number at the beginning.

gzip is open source, so you can just look at the code.

-- glen

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#459

What are the *first* two bytes of the .z file?

Mark

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#470

On Jul 23, 6:09 am, Mark Adler <mad...@alumni.caltech.edu> wrote:
> What are the *first* two bytes of the .z file?
>
> Mark

Hmm - not sure why I didn't spot that.   The first two bytes are 1e1f
according to od -x.

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#471

On Jul 23, 6:09 am, Mark Adler <mad...@alumni.caltech.edu> wrote:
> What are the *first* two bytes of the .z file?
>
> Mark

Sorry - forgot to page the output from od.

od -x says:

0000000     1e1f    0000    a203    0006    0400    0306    2000
312e

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#474

Good.  It has the prefix for a pack file.

So my other question was: what happens when you try to use gzip to 
unpack?  What error do you get?

Mark

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#475

This has been resolved.  The "gzip" being used was not actually gzip, 
but a homegrown gzip on NetBSD, written by Matthew R. Green, that uses 
zlib.  It's unpack apparently doesn't work.  gzip's does.

Mark

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