Switch logging (or whatever) based on a signal in ruby.

logswitch.rb

#!/usr/bin/env ruby
#
#   terminal1> ruby logswitch.rb
#   terminal2> kill -s USR1 $(cat pid_file)
#

File.open("pid_file", "w") do |io|
  io.puts Process.pid
end

char = "."
Signal.trap("USR1") do
  char = (char == "." ? "!" : ".")
end

while true
  $stdout.printf char
  $stdout.flush
  sleep 1
end