Stuart Prescott writes ("Re: Please add lzip support in the repository"): > > What is `apt-helper cat-file' and how does it help ? > > On stretch: > > $ apt-file search apt-helper > apt: /usr/lib/apt/apt-helper
Ah. I looked on PATH. I expect "Front door" programs to be on PATH nowadays. > $ /usr/lib/apt/apt-helper download-file > http://deb.debian.org/debian/dists/sid/main/binary-amd64/Packages.xz > Packages.xz > Get:1 http://deb.debian.org/debian/dists/sid/main/binary-amd64/Packages.xz > [7,547 kB] > Fetched 7,547 kB in 5s (1,446 kB/s) > > $ /usr/lib/apt/apt-helper cat-file Packages.xz | less So this is not really a replacement for the impugned compression regexps because * it's not available in stable (some of us care about backportability and supporting stable users) * it involves invoking a command and parsing the output to get trivial information which should be available as a simple variable in a scripting language * it provides only a more-cooked interface than is probably wanted A better answer would be the perl function Dpkg::Compression::compression_guess_from_filename which is fairly easy to use and has been available for a long time. Useable something like this: https://browse.dgit.debian.org/dgit.git/tree/dgit#n2163 Or if you just want to strip the compression extension then \.([^\.]+) and call compression_guess_from_filename on $1 and see if it's undef. See for example https://manpages.debian.org/wheezy/libdpkg-perl/Dpkg::Compression.3.en.html Ideally other languages should have something similar. Ian.