# File lib/whenever/command_line.rb, line 67
    def write_crontab(contents)
      command = ['crontab']
      command << "-u #{@options[:user]}" if @options[:user]
      command << "-"

      IO.popen(command.join(' '), 'r+') do |crontab|
        crontab.write(contents)
        crontab.close_write
      end

      success = $?.exitstatus.zero?

      if success
        action = 'written' if @options[:write]
        action = 'updated' if @options[:update]
        puts "[write] crontab file #{action}"
        exit(0)
      else
        warn "[fail] Couldn't write crontab; try running `whenever' with no options to ensure your schedule file is valid."
        exit(1)
      end
    end