Re: Option wanted for gzip

[Raoul Behrend]

Hello Bob and the gzip-Team,

Many thanks for the follow up of my proposition.

For the application I devellope, I have to collect gzipped astronomical images, 
calibrate (after gunzipping) them, and archive the raw image in a compressed 
manner. The new modified ones are also archived after a gzipping, while a copy of 
the unzipped processed images are sent to a second pass of reduction.

So, the flux is as below.
raw.fit.gz  - archived
            - gunzipped - modified by first pass
                  - gzipped and archived
                  - second pass of processing

The first and second pass usually are not done at the same moment, as some data 
have to be collected and analysed before the second pass. Sometimes, two ot three 
passes of the whole files in necessary.

Due to the huge size of the data on the disks, I 'd like to keep to a minimum hard 
disk works: this can be done using a kind of keeping of the entry file in its 
current state at the end of the decompression or compression operations.

bzip2 had a -k option which do the work nicely. I looked into the gzip source 
file, and saw that -k is attributed to a pkzip compression scheme (but apparently 
desactivated), so a different option is to be chosen: could it be -K ?

I have difficulties to work with C in a secure way - I basically learned Fortran, 
Pascal and Ada. So I'd like some help to manage such an item.

Remark: the naming of the file is unpredictable, so a special unportable macro 
should be developped if one want to use the < and > redirectors to specify the 
output name, as suggested in your first answer.

Can you help me ?

Kindest regards, Raoul



Bob Proulx a écrit:

> Hello Raoul,
>
> Please keep the mailing list address in the CC list so that others may
> participate in the discussion.
>
> Raoul Behrend wrote:
>
> > Unfortunately, I have to do it on several hundreds of astronomical images 
> > per night, both on linux and on wxp.
>
>
> I don't understand why that would lead to a special problem in this
> case.  Are you concerned about some feature in particular?  Please
> explain so that we may help.
>
>
> > I'm pretty sure that the delete/not delete mechanism at the end of 
> > (de)compression could be managed in ~20 lines and that it would be more 
> > portable than doing special macros to do it.
>
>
> Now I am twice confused because your original request was for a way to
> keep the file and also decompress it avoiding the default gzip/gunzip
> behavior of deleting it and here you are asking for a way to delete
> the file?  As I read things that is the default behavior that you were
> asking to avoid!  If you want to delete the file then simply let
> gzip/gunzip delete the file after decompressing it.  Plus I did not
> suggest using any "macros".  I did not suggest using anything that was
> not portable.  Therefore I am very confused.
>
> Please explain your concerns.  If you could perhaps give an example of
> what you are trying to do then I am sure that it would make things
> more clear.  If using the command as suggested does not work for you
> could please say some words about why?
>
> Using the shell to redirect the output of the command is portable.  I
> think that would be the most portable answer.  Because if you were to
> add a special option then you would only be able to operate on systems
> that had your special version available.  If you simply redirect the
> output then it will work everywhere.
>
> Bob
>
> Raoul Behrend wrote:
>
> > Hello,
> >
> > Thank you for your fast and kind answer.
> >
> > Unfortunately, I have to do it on several hundreds of astronomical images 
> > per night, both on linux and on wxp.
> >
> > I'm pretty sure that the delete/not delete mechanism at the end of 
> > (de)compression could be managed in ~20 lines and that it would be more 
> > portable than doing special macros to do it. I'll look in the gzip source 
> > code how it can be implemented.
> >
> > Have a plesant sunday. Cheers, Raoul
> >
> >
> >
> > Bob Proulx a écrit:
> >
> >
> > > Raoul Behrend wrote:
> > >
> > >
> > > > I would really appreciate the presence of a -k option, like in bzip2, 
> > > > which keeps the original files while making the (de)compression ? Is it 
> > > > possible ?
> > >
> > >
> > > Do any of the following do what you want?
> > >
> > > gzip -dc file1 > file2
> > > gunzip -c file1 > file2
> > > gzip -d < file1.gz > file2
> > > gunzip < file1.gz > file2
> > >
> > > Bob

--

Dr Raoul Behrend

Observatoire de Genève       Geneva Observatory
CH-1290 Sauverny             CH-1290 Sauverny
Suisse                       Switzerland

address@hidden
http://obswww.unige.ch/~behrend

Herbe à Nicot? Herbe à nigauds!