What do these files do when you run them with Ruby?

command-quiz-all-in-one.rb

#!/usr/bin/ruby
# Ruby Gotcha Quiz, by Martin Vidner
# Aimed at people who have written something in Ruby already

def command(s)
  system(s)
end

command   "echo A"

command <<EOS
echo B
EOS

# The 1st program ends here. Will it work?

command = "echo C"

command   "echo D"

# The 2nd program includes the 1st program and ends here. Will it work?

command <<EOS
echo E
EOS

# The 3rd program includes the above and ends here. Will it work?

command <<EOS
ls -l -a
EOS

# The 4th program includes the above and ends here. Will it work?

# If a program does not work, what kind of error occurs?
# - syntax error, the interpreter/compiler complains before running it
# - runtime error, it aborts while running
# - logic error, it runs without aborting but does something else than intended
# - style error, it works but your team will not accept it into the shared repo

command-quiz1.rb

#!/usr/bin/ruby
def command(s)
  system(s)
end

command   "echo A"

command <<EOS
echo B
EOS

command-quiz2.rb

#!/usr/bin/ruby
def command(s)
  system(s)
end

command   "echo A"

command <<EOS
echo B
EOS

command = "echo C"

command   "echo D"

command-quiz3.rb

#!/usr/bin/ruby
def command(s)
  system(s)
end

command   "echo A"

command <<EOS
echo B
EOS

command = "echo C"

command   "echo D"

command <<EOS
echo E
EOS

command-quiz4.rb

#!/usr/bin/ruby
def command(s)
  system(s)
end

command   "echo A"

command <<EOS
echo B
EOS

command = "echo C"

command   "echo D"

command <<EOS
echo E
EOS

command <<EOS
ls -l -a
EOS

@bmwiedemann this is the problem that we hit when we catted the chef files in crowbar-openstack