What are the respective files when specifying a software source suite by an exact path?

Question

man 5 sources.list tells: "suite can specify an exact path, in which case the components must be omitted and suite must end with a slash (/)." Can you give an example of such a source specification and what are the respective files under /var/lib/apt/lists? If you can tell something more general, even better.

Answer 1

I found an example at http://cran.rstudio.com/bin/linux/ubuntu/

In 24.04 (noble) I applied current recommendations and tried

$ sudo add-apt-repository -S "deb [signed-by=/etc/apt/keyrings/cran_ubuntu_key.asc] https://cloud.r-project.org/bin/linux/ubuntu $(lsb_release -cs)-cran40/"
Invalid sources.list line: 'deb [signed-by=/etc/apt/keyrings/cran_ubuntu_key.asc] https://cloud.r-project.org/bin/linux/ubuntu noble-cran40/'

But I could install the repository by

$ wget -qO- https://cloud.r-project.org/bin/linux/ubuntu/marutter_pubkey.asc | sudo tee -a /etc/apt/keyrings/cran_ubuntu_key.asc
$ sudo bash -c 'echo "deb [signed-by=/etc/apt/keyrings/cran_ubuntu_key.asc] https://cloud.r-project.org/bin/linux/ubuntu $(lsb_release -cs)-cran40/" > /etc/apt/sources.list.d/cran.list'
$ sudo apt update

Then

$ cd /var/lib/apt/lists/
$ ls -1 cloud.r-project.org*
cloud.r-project.org_bin_linux_ubuntu_noble-cran40_InRelease
cloud.r-project.org_bin_linux_ubuntu_noble-cran40_Packages

So it seems to connect the URI part without https?:// part and suite specification with _ and replace all / by _ in the string before adding the usual suffixes.