Ruby HTTP Server
Akin to SimpleHTTPServer (module) in Python 2, server.http in Python 3.
-r requires the named library before executing, -run == require un.rb which is a set of utilities to replace common UNIX commands in Makefiles etc.
Executes command as one line of Ruby source. Several -e's are allowed, and the commands are treated as multiple lines in the same program. If program file is omitted when -e is present, execution stops after the -e commands have been run.
Run Rack Server, current working directory as server document root
Run a simple HTTP Server, currently working directory as document root