cat-p

#!/usr/bin/env ruby
## Swipe stdout from another program by pid (using strace -p)
# Test by running
# echo $$; while sleep .5; do echo '"\"; system("echo egads"); \""'; done
# (observe the pid that comes out at the start)
pid = ARGV[0].to_s or fail "Need a pid to trace."
cmd = ['strace', '-p', pid, '-e', 'write', '-s', '999999', :err=>[:child, :out]]
IO.popen cmd do |io|
  io.each_line do |line|
    line.sub /^write\(1, "(.+)", \d+\)/ do
      puts eval %{"#{$1}"}
    end
  end
end