Linux program, it mimics basic behaviour of ls but is simpler and worse, I have no idea why would you even use it but hey
so basically you want to download it and run install.sh, to do it follow an instruction below
$ mkdir ~/sd
$ cd ~/sd
$ git clone https://github.com/NnnNnn2/sd.git
$ cd sd
$ chmod +x install.sh
$ ./install.sh
if it doesn't work you can compile the C file using gcc
$ gcc sd.c -o sd
and then try to run install.sh again, if that doesn't work you can manually install said file
$ sudo install ./sd /usr/bin