irb interactive ruby and ruby files

commandline session

$ 4.2.20 9 508---> irb
irb(main):001:0> 10+10
=> 20
irb(main):002:0> 34*5
=> 170
irb(main):003:0> 9-8
=> 1
irb(main):004:0> ()
=> nil
irb(main):005:0>
$ 4.2.20 12 511---> ruby sum.rb
3
$ 4.2.20 13 512---> cat sum.rb
a = 1 + 2
puts a
$ 4.2.20 14 513--->

$ 4.2.20 15 514---> irb
irb(main):001:0> Dir.entries('/home/jeffrin/shelter/symmel/')
=> ["Docs", "books", "..", "https:", "debian-howtos", "language", ".git", "linux", "ovlfose", "bugs-general", "Algorithms", "firewall", "config-files", "README", "beautifulwork", ".", "bookmark"]
irb(main):002:0>