How to fix the Mac error – “You can’t open the application because it may be damaged or incomplete”

All of a sudden my husband’s macbook could no longer open any OSX apps, including Safari, App Store, iMovie, Photos, etc. Once attempted to be opened, the app icons show a ? instead of the usual app icon. He would then get the following error:

You can’t open the application because it may be damaged or incomplete

After several searches on Google, I stumbled upon this forum with many different solutions. The one that worked for him (and luckily quite simple) is to clear a few cached files using the following steps:

1. On Finder, Go > Go to folder > /var/folders 
2.  You will see two letter folders like the below. Apart from zz, open each two letter folder and it’s subfolder until you find folders labeled with O, C, and T. Clear the contents of each of the O, C, T folders. 
3.  Restart your Mac

Once restarted, the apps on the macbook opened without issues an no longer showing the ? icons.

Hope this helps anyone!