How to Find the Reverse Dependency of a Package

Today, there was a nice little discussion on vacdec’s GitHub project about what needs to be installed to make the barcode scanner pyzbar work on Ubuntu and MacOS.

The original poster proposed to install zbar on both operating systems.

zbar for Ubuntu comes with a ton of dependencies.

So I had a look at my installed packages…

❯ apt list --installed | grep zbar
libzbar0/bionic,now 0.10+doc-10.1build2 amd64 [installed]

… which only revealed the libzbar0 library.

As vacdec still works like a charm, installing zbar does not seem to be necessary.

But how did libzbar0 land on my pc? I could not recall installing it manually.

The Solution

❯ apt-cache rdepends --installed libzbar0
libzbar0
Reverse Depends:
  gstreamer1.0-plugins-bad
  gstreamer1.0-plugins-bad