MacOS – Shell script to determine the file size in a folder recursively

sudo -b makes the application run in the background.

sudo -b appThatNeedsPort25

Unlike with sudo appThatNeedsPort25 &, sudo itself will run in the foreground, so you'll have no issues with its password prompt. Note that sudo also has a -A option to make it ask for a password through a GUI instead of in the terminal, you can use this when sudo isn't running from a terminal.

This won't work for a signed app, but here's how I was able to get this to work:

1. Create a copy of the app you're trying to modify in case something goes wrong. (⌘D in Finder) For my example here, I modified the non-app store version of VectorDesigner

2. In Terminal, cd /Applications/VectorDesigner.app/Contents/MacOS

3. mv VectorDesigner VectorDesigner\ copy (substitute the name of your app here

4. pico VectorDesigner (or your editor of choice) and add the contents of your script.

   I used this script

    #!/bin/sh
    osascript -e "tell Application \"Finder\" to display alert \"Hello World\""
    /Applications/VectorDesigner.app/Contents/MacOS/VectorDesigner\ copy
   

   The important thing is for the last line to call the renamed executable.

5. chmod a+x VectorDesigner

Now, when I double-click the VectorDesigner icon, I get the "Hello World" window, then it launches the original program.