SL (Steam Locomotive) runs across your terminal when you type "sl" as you meant to type "ls". It's just a joke command, and not useful at all.
% sl --help
Usage:
sl <options>
Options:
-a Accident
-F Fly
-d Show logo
-c Show C51
-G Show TGV
-t <time>
--time <time> Set animation time (miliseconds)
Returns:
1 Invalid option
2 Invalid <time>
3 Missing <time>
4 Aborted because 1 sec/frame takes forever
Timing 2022 Ronald Chu
TGV Fork 2019 Matthias Gatto
sl 5.03 Copyright 1993,1998,2014 Toyoda Masashi