This blog shows how to use the API on Ubuntu’s “Launchpad” package creation system to retrieve metadata, like the date a patch was created.

Fetching Metadata from Launchpad

Ubuntu has four main, official repositories where packages are stored. You typically run apt or apt-get to find and download the latest packages. You can look through these repositories and search for packages though a web browser at https://packages.ubuntu.com/.

Canonical, the makers of Ubuntu, use a system called Launchpad to create the packages and store them in the repositories. You can search through Launchpad with a browser and find information like a package’s detailed history. Launchpad also has a poorly documented API that lets you retrieve this same information.

This example shell program uses HTTP requests to the API to retrieve package creation dates. This specific script reports dates for packages in the updates or security pockets of Ubuntu 20.04 (“Focal”) that the apt utility says have available updates.

The key line showing this fetch from the API is:

sources_json=$(curl -s "https://api.launchpad.net/1.0/ubuntu/+archive/primary?ws.op=getPublishedBinaries&exact_match=true&$pocket=Security&status=Publi
shed&distro_arch_series=https://api.launchpad.net/1.0/ubuntu/focal/$architecture&binary_name=$package")

Running this script (./package-date-launchpad) results in output like this:

Package: openssh-client
Pocket: focal-updates
Architecture: amd64
New Version Available: 1:8.2p1-4ubuntu0.3
Dates for all versions:
"openssh-client Published 1:8.2p1-4ubuntu0.3 2021-08-13T07:23:55.517155+00:00"
"openssh-client Published 1:8.2p1-4ubuntu0.2 2021-03-10T14:33:26.528429+00:00"
"openssh-client Published 1:8.2p1-4 2020-03-30T13:43:28.232861+00:00"

Package: openssl
Pocket: focal-updates
Architecture: amd64
New Version Available: 1.1.1f-1ubuntu2.5
Dates for all versions:
"openssl Published 1.1.1f-1ubuntu2.5 2021-08-13T07:23:55.517155+00:00"
"openssl Published 1.1.1f-1ubuntu2.3 2021-03-25T14:33:39.771591+00:00"
"openssl Published 1.1.1f-1ubuntu2 2020-04-21T22:13:20.156919+00:00"

As you can see, this shows not only the most recent version of the package available, but also all older versions.