tar -k --keep-old-files extraction problem

somae · 01-28-2009, 03:38 AM

I've been trying to extract an archive using tar and want to prevent it from overwriting any files with the same names using

Code:

tar -xkvf --keep-old-files (file.tar)

but it keeps giving errors.

Was wondering how to do it?

Thanks.

colucix · 01-28-2009, 03:47 AM

First don't put --keep-old-files AND -k. They are two forms (long and short) of the same option. Second invert the groups of option and it should work. This is because the -f option accepts as argument the name of the archive, so that the part f --keep-old-files is interpreted as the name of the archive. In summary the solution is either one of the following

Code:

$ tar --keep-old-files -xvf file.tar
$ tar -xkvf file.tar

somae · 02-02-2009, 02:44 AM

Thanks.

One thing that confused me is that there are several alternatives for the "-k" option - some of which are the opposite of what I want.

I assume there is some interactive dialog that comes up when you use "-k"?

I just tried the

Code:

 tar --keep-old-files -xvf file.tar

method and got alot of

Quote:

Cannot open: File exists
tar: Skipping to next header

which ended with

Quote:

tar: Error exit delayed from previous errors

.

colucix · 02-02-2009, 02:57 AM

Not an interactive dialog, but just an error message. You can either chose --overwrite to force overwriting OR --keep-old-files to prevent this behavior. That is your choice is made prior to run the extraction of the archive, not in run time.

What do you mean for "there are several alternatives for the -k option"? To me the -k option is unique.

somae · 02-03-2009, 01:31 AM

Quote:

Originally Posted by colucix

What do you mean for "there are several alternatives for the -k option"? To me the -k option is unique.

The "tar --help" file says this:

Code:

 -k, --keep-old-files       don't replace existing files when extracting
      --keep-newer-files     don't replace existing files that are newer than
                             their archive copies
      --no-overwrite-dir     preserve metadata of existing directories
      --overwrite            overwrite existing files when extracting
      --overwrite-dir        overwrite metadata of existing directories when
                             extracting (default)
      --recursive-unlink     empty hierarchies prior to extracting directory
      --remove-files         remove files after adding them to the archive

It makes it look like these are all functions of "-k".

colucix · 02-03-2009, 02:41 AM

Quote:

Originally Posted by somae

It makes it look like these are all functions of "-k".

Nope. It tells that the -k option is the short form of --keep-old-files, while the other options listed do not have a short form. Indeed they are all related to the behavior of tar in case of already existing files with the same name, but -k is --keep-old-files only.

I see now the reason why you used both -k and --keep-old-files in the same command line. Well, the help can be confusing, but keep in mind that an option may accept one or more arguments, but never accept another option as argument, that is a string beginning with - or --.

Code:

-k, --keep-old-files       don't replace existing files when extracting

The comma tells you they are two different alternatives of the same option.

colucix · 02-03-2009, 02:45 AM

Quote:

Originally Posted by somae

tar: Error exit delayed from previous errors

This is the normal behavior. If one or more files already exist, the file(s) are not extracted from the archive and tar gives an error message and an exit status different from zero.

ciotog · 02-27-2009, 03:34 PM

If you've specified "keep" or "-k" then tar shouldn't complain that a file already exists, it should ignore it. I think that's the crux of the problem.

ciotog · 02-27-2009, 03:51 PM

I've been reading through the info pages, and this is what is says verbatum:

Quote:

To be even more cautious and prevent existing files from being replaced, use the `--keep-old-files' (`-k') option. It causes `tar' to refuse to replace or update a file that already exists, i.e., a file with the same name as an archive member prevents extraction of that archive member. Instead, it reports an error.

So evidently it's by design.