Running a shell subprocess is surprisingly hard in ruby

shell_execute.rb

require "open3"

def execute_shell(command, verbose: false)
  Rails.logger.info "[SHELL] #{command}"

  # see: https://nickcharlton.net/posts/ruby-subprocesses-with-stdout-stderr-streams.html
  # see: http://stackoverflow.com/a/1162850/83386
  output = []
  Open3.popen3(command) do |stdin, stdout, stderr, thread|
    # read each stream from a new thread
    readers = { :out => stdout, :err => stderr }.map do |key, stream|
      Thread.new do
        until (raw_line = stream.gets).nil? do
          line = raw_line.strip
          next if line.empty?

          case key
          when :out
            Rails.logger.debug "[STDOUT] #{line}" if verbose
            output << line
          when :err
            Rails.logger.warn "[STDERR] #{line}"
          end
        end
      end
    end

    thread.join # don't exit until the external process is done
    readers.map(&:join) # give reader threads a chance to clear out open buffers
  end
  output
end