Parameter Hunting

Preface: Often in our line of work, the answer requires a little digging. The purpose of this post is to walk you through my thought process in an effort to illustrate how I go about linking disparate pieces of information together to arrive at a solution.

Last week, I was tasked with creating a script to silently uninstall an application across a managed environment with nearly 800 endpoints spanning multiple physical locations and at least 3 separate domains – that was the easy part.

The hard part was that this application was installed as .EXE file rather than an MSI package (i.e. I couldn’t just script out msiexec /x…). While it did have an uninstall.exe file, this called the GUI uninstaller, and I wasn’t about to have someone go through and click ‘next’ ‘next’ ‘next’ for each one!

Many .EXE’s have CLI parameters you can invoke, so I started with the usual suspects:

  • uninstall.exe /?
  • uninstall.exe –?
  • uninstall.exe /help
  • uninstall.exe -help
  • uninstall.exe –help

None of these worked (it wouldn’t be post-worthy if it was that easy)!

Next, I went looking for any documentation that was available for the application – I had:

  • Googled the manufacturer for any documentation/examples – nada
  • Read all of the .txt files in the installation folder – zilch
  • Reviewed the .ini and .config files for clues, saw something vaguely useful – a reference to “NSIS” – tabled it and kept looking

Finally, I decided to use SysInternals Process Explorer to inspect the application:

  1. Run the application you want to inspect
  2. Open Process Explorer (as administrator)
  3. Find the application on the list
  4. Right click on the application and select “Properties…”
  5. Under the “Image” tab, you will see a field for “Command line:”

The Command line will tell you what commands/switches it runs. In this case, the uninstall.exe was running with the switch, “_?=C:\Program Files\[Application Name]”.

I decided to Google the switch itself, which lead me to the Nullsoft Scriptable Install System documentation. I was able to work out that the application used NSIS to create the installer/uninstaller package, and through that, found some examples, one of which (/S) runs the installer/uninstaller silently!

This was exactly what I was looking for! All I had to do was append the command with “/S”, and sure enough, it removed the application without any prompts or launching the GUI!

It just goes to show that persistence pays off, and a little time and effort can save your organization/client hundreds of hours of manual work.

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