Omaha Registry

Omaha Client writes a progress of update process in registry keys. So you just need to launch an update process and periodically check special keys as noted below. This approach is the easiest and universal way because you can use it in almost all programming languages even in Batch Script.

1. Execute a new process inside the application.
   GoogleUpdate.exe /machine /ua /installsource ondemand

2. Read registry keys values:

• the current installed version
  HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\<Company>\Update\Clients\{<App GUID>}

  name
  pv
  

• the application update progress
  HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\<Company>\Update\ClientState\{<App GUID>}\CurrentState

  DownloadProgressPercent
  DownloadTimeRemainingMs
  ...
  StateValue
  

You can find some examples by following this link