exempi software package provides command line tool to manipulate XMP metadata, 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 exempi
exempi is installed in your system.
Make ensure the exempi package were installed using the commands given below,
$ sudo dpkg-query -l | grep exempi *
You will get with exempi package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Graphics |
| Package | exempi |
| Version | 2.3.0-2 |
| Description | command line tool to manipulate XMP metadata |
| Sub Section | Graphics |