Another gsub/regex problem

I've got a load of data with newlines (\n) scattered throughout, I want 
to remove all the newlines from this file, before

filename.each do |line| ... end

I'm playing with various combinations for gsub! and unfortunately I 
can't strip all of them out

filename.to_s.gsub!(/\n/, '')

removes some of them, the problem is

...ahh

input.to_s.gsub!(/(.*)\n(.*)/,'\1\2')

nope still doesn't work

Any ideas - (i'm looking through the pickaxe1 book but can't find 
anything) - off to google now

Kev