Can you use tar to apply a patch to an existing web application?

Question

Patches are frequently released for my CMS system. I want to be able to extract the tar file containing the patched files for the latest version directly over the full version on my development system. When I extract a tar file it puts it into a folder with the name of the tar file. That leaves me to manually copy each file over to the main directory. Is there a way to force the tar to extract the files into the current directory and overwrite any files that have the same filenames? Any directories that already exist should not be overwritten, but merged...

Is this possible? If so, what is the command?

Answer 1

Check out the --strip-components (or --strippath) argument to tar, might be what you're looking for.

EDIT: you might want to throw --keep-newer into the mix, so any locally modified files aren't overwritten. And I would suggest testing new releases on a development server, then using rsync or subversion to carry over the changes.

Answer 2

The option '--strip-components' allows you to trim parts of the embedded filenames. With that it is possible to do what you want.

For more help check out http://www.gnu.org/software/tar/manual/html_section/transform.html

Answer 3

I tried getting --strip-components to work and, while I didn't try that hard, I didn't get it working. It kept flattening the directory structure. In searching, I came across the following command that seems to do exactly what I want:

pax -r -f patch.tar -s'/patch\///'

It's not tar, but hey, it works... Replace the words "patch" with whatever your tar file name is.