gap-io software package provides low level C library IO bindings for GAP, 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 gap-io
gap-io is installed in your system.
Make ensure the gap-io package were installed using the commands given below,
$ sudo dpkg-query -l | grep gap-io *
You will get with gap-io package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Mathematics |
| Package | gap-io |
| Version | 4.4.6+ds-2 |
| Description | low level C library IO bindings for GAP |
| Sub Section | Math |