ddir software package provides display hierarchical directory tree, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install ddir
ddir is installed in your system.
Make ensure the ddir package were installed using the commands given below,
$ sudo dpkg-query -l | grep ddir *
You will get with ddir package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Utilities |
| Package | ddir |
| Version | 2016.1029+gitce9f8e4-1 |
| Description | display hierarchical directory tree |
| Sub Section | Utils |