[kwlug-disc] tar --directory help please

[Chris Irwin]

On Wed, Jun 04, 2025 at 10:33:42AM -0700, Ronald Barnes via kwlug-disc wrote:
>
>I've always found the --directory option for `tar` to be so 
>frustrating as to be worse than useless.
>
>
>Can someone explain this behaviour?

-C/--directory changes to a specific directory before processing files 
aftere it. It's useful in only specific scenarios where you want your 
tar to be relative to a specific base directory (or include files from 
mutiple directories, but in the same shared path within the tar), and 
you know the contents by name.  Your file list can't use shell wildcards 
(because tar will be working outside of $PWD, bash can't expand them), 
and tar doesn't accept wildcards itself (so you can't pass 
mail\*.service as your file list).

For example, if you wanted to tar up the files relative to the systemd 
directory you specified, you could:

     $ tar -cf /tmp/test.tar \
         --directory /etc/systemd/system/ \
         mailman3.service \
         mailman3-web.service

Personally, in this scenario I always found it easier to use pushd/popd 
in scripts since you're only including files relative to one directory.  
It's less weird, and easier to read. As a bonus, you can use shell 
wildcards again.

     $ pushd /etc/systemd/system
     $ tar -czf /tmp/test.tar mailm*
     $ popd

Both of the above provide the same contents:

     $ tar -tf /tmp/test.tar
     mailman3.service
     mailman3-web.service


All that said, it looks like in your example, you're trying to preserve 
the full path (hence --directory=/).  You don't need to use --directory 
for that. Just provide the full path to the files, that will be 
preserved in the zip.

     $ tar -cf /tmp/test.tar /etc/systemd/system/mailm*

That provides the full path with no --directory required:

     $ tar -tf /tmp/test.tar
     etc/systemd/system/mailman3.service
     etc/systemd/system/mailman3-web.service

I also use filelists (such as your find example in another reply), but 
usually for more complex tasks than this (ex: to tar files that match a 
grep regex or something else externally driven).

-- 
Chris Irwin

email:   chris at chrisirwin.ca
  xmpp:   chris at chrisirwin.ca
   web: https://chrisirwin.ca