Fixes agiledivider#141: Check for newlines before writing hosts file.

lib/vagrant-hostsupdater/HostsUpdater.rb

@@ -137,14 +137,7 @@ def addToHosts(entries)
 
  @ui.info "[vagrant-hostsupdater] Writing the following entries to (#@@hosts_path)"
  @ui.info "[vagrant-hostsupdater] " + entries.join("\n[vagrant-hostsupdater] ")
- if !File.writable_real?(@@hosts_path)
- @ui.info "[vagrant-hostsupdater] This operation requires administrative access. You may " +
- "skip it by manually adding equivalent entries to the hosts file."
- if !sudo(%Q(sh -c 'echo "#{content}" >> #@@hosts_path'))
- @ui.error "[vagrant-hostsupdater] Failed to add hosts, could not use sudo"
- adviseOnSudo
- end
- elsif Vagrant::Util::Platform.windows?
+ if Vagrant::Util::Platform.windows?
  require 'tmpdir'
  uuid = @machine.id || @machine.config.hostsupdater.id
  tmpPath = File.join(Dir.tmpdir, 'hosts-' + uuid + '.cmd')
@@ -154,10 +147,22 @@ def addToHosts(entries)
  sudo(tmpPath)
  File.delete(tmpPath)
  else
- content = "\n" + content + "\n"
- hostsFile = File.open(@@hosts_path, "a")
- hostsFile.write(content)
- hostsFile.close()
+ # Check if the file is missing a newline before writing to it.
+ if !system("tail -c1 #@@hosts_path | read -r _")
+ content = "\n" + content
+ end
+ if !File.writable_real?(@@hosts_path)
+ @ui.info "[vagrant-hostsupdater] This operation requires administrative access. You may " +
+ "skip it by manually adding equivalent entries to the hosts file."
+ if !sudo(%Q(sh -c 'echo "#{content}" >> #@@hosts_path'))
+ @ui.error "[vagrant-hostsupdater] Failed to add hosts, could not use sudo"
+ adviseOnSudo
+ end
+ else
+ hostsFile = File.open(@@hosts_path, "a")
+ hostsFile.write(content)
+ hostsFile.close()
+ end
  end
  end