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Driving an External Process with popen
CodeExpectedActual
%x{whoami}
 "leonardr\n" "leonardr\n" 
puts %x{ls -a empty_dir}
 
.
..
 






IO.popen('tail -3', 'r+') do |pipe|
  1.upto(100) { |i| pipe << "This is line #{i}.\n" }
  pipe.close_write
  puts pipe.read
end


This is line 98.
This is line 99.
This is line 100.


This is line 98.
This is line 99.
This is line 100.






IO.popen('-', 'r+') do |child_filehandle|
  if child_filehandle
    $stderr.puts "I am the parent: #{child_filehandle.inspect}"
    child_filehandle.puts '404'
    child_filehandle.close_write
    puts "My child says the square root of 404 is #{child_filehandle.read}"
  else
    $stderr.puts "I am the child: #{child_filehandle.inspect}"
    number = $stdin.readline.strip.to_i
    $stdout.puts Math.sqrt(number)
  end
end


I am the child: nil
I am the parent: #<IO:0xb7d25b9c>
My child says the square root of 404 is 20.0997512422418


My child says the square root of 404 is