SIGKILL cannot be trapped

input-multiplexer.rb

# input-multiplexer.rb stdout=file1 stdout=name_2=file2 stderr=name_3=file3 ...
#   Merges the specified files together into stdout or stderr (as specified)
#
#   Example output:
#      file1| first line from file1
#      file1| the next line from file1
#     name_3| first line from line3
#     name_2| first line from line2
#      file1| the next line from file1
#     ...
#
#   Uses select(), so files should be pipes/FIFOs etc.
#   If you need `tail -f` style output on a normal file, make a pipe:
#     input-multiplexer.rb stdout=file=<(tail -f file) ...

if __FILE__ == $0
  if ARGV.empty? or ARGV.include?('--help') or ARGV.include?('-h')
    puts File.readlines(__FILE__).take_while{|i| i.start_with?('#')}
    exit
  end

  %w[ INT TERM CHLD ].each{|sig| Signal.trap(sig, 'EXIT') }

  args = ARGV.map{|a| a.split('=', 3)}
  stream = args.map(&:first)
  names = args.map{|a| a[2] ? a[1] : File.basename(a[1])}
  files = args.map(&:last)

  stream = {'stdout'=>STDOUT, 'stderr'=>STDERR}.values_at(*stream)
  raise "Missing stdout= or stderr=" unless stream.all? and stream.any?

  colours = (31..36).to_a + (91..96).to_a
  width = names.map(&:length).max

  io = files.map{|f| open(f, File::NONBLOCK)}
  mapping = Hash[io.zip(files.zip(names, stream, colours.cycle))]
  loop do
    IO.select(io)[0].each do |r|
      path, name, out, col = mapping[r]

      if r.eof?
        r.close
        r.reopen(path, File::NONBLOCK)
      else
        out.printf("\x1b[%im%*s|\x1b[m %s\n", col, width, name, r.gets.chomp)
        out.flush
      end
    end
  end
end