=begin

An exception may be thrown by this class if it's asked to get
the size of a file that does not exist. If an exception is
raised from the level at which if occurs, then it needs to be
caught and rescued by the parent too if you don't want your
program to crash at that higher level.

Notice that we've set the message to go along with the exception
that we've raised, and we can access it via the $! special global
variable.

=end

class Mytest
        def initialize(filename)
                @filename = filename
                @cached = false
        end
        def getsize
            return @store if @cached
            begin
                size = File.size(@filename)
                @store = size
                @cached = true
                return size
            rescue
                raise "No access to file #{@filename}"
            end
                end
end

# If the file you have loaded this code from is the same
# as the name of the command you are running ...

if __FILE__ == $0
rq = Mytest.new("../fred")
rq2 = Mytest.new("../henry")
begin
s1 = rq.getsize()
s2 = rq2.getsize()
rescue
puts "not all there [[#{$!}]]"
end
puts "#{s1} #{s2}"

else
puts "Mytest class loaded"
end

__END__

Sample output:

Dorothy-2:d3 grahamellis$ ruby mighty.rb
not all there [[No access to file ../henry]]
98
Dorothy-2:d3 grahamellis$