> # Output irb history to named file
> def dumphist(path="irb.log")
>   File.open(path, 'w') do |file|
>     Readline::HISTORY.each do |line|
>       file.puts line unless /^\s*dumphist/ =~ line
>     end
>   end
> end

Is Readline a 1.8 thing?

D:\ruby\bin>more .irbrc
# Output irb history to named file
def dumphist(path="irb.log")
  File.open(path, 'w') do |file|
    Readline::HISTORY.each do |line|
      file.puts line unless /^\s*dumphist/ =~ line
    end
  end
end

D:\ruby\bin>irb
irb(main):001:0> puts VERSION
1.6.6
nil
irb(main):002:0> dumphist
NameError: uninitialized constant Readline
        from ./.irbrc:4:in `dumphist'
        from ./.irbrc:3:in `open'
        from ./.irbrc:3:in `dumphist'
        from (irb):2


Chris
http://clabs.org