If you have purchased programs through the App Store, then updates for them will also be available through the store. The same goes for OS X, where Apple has combined its core OS update process with the App Store. For the most part the update services through the App Store work well; however, there may be times when the App Store will hang or otherwise not complete a desired update, even after repeated attempts to do so.

There are a couple of approaches you can take to clear such problems if they occur. First, quit the App Store, or force-quit it if the program is unresponsive (do this by pressing Option-Command-Escape to bring up the force-quit menu). Then you can try the following options:

Clear the App Store updates folder

If you are having a problem with a specific update showing an error when it is downloaded, then go to the Macintosh HD > Library > Updates folder and remove the downloaded package pertaining to the update. Optionally, since nothing in this directory is vital, and will only be replaced when you re-launch the App Store, remove the entire contents of this directory to ensure any damaged contents is refreshed by the App Store when it is next run.

Clear the App Store caches

As with many programs, the App Store will save temporary files in a couple of hidden temporary and cache directories on your system. These should be refreshed by the application when it runs, but it is possible damage to them could interfere with how the program runs. Therefore you can try manually removing them by doing the following:

1. Open the Terminal and run the following command (copy and paste it):

   open $TMPDIR../C

2. Locate any folder that begins with “com.apple.appstore” and remove it.
3. Go back to the Terminal and run the following command to open the temporary files folder:

   open $TMPDIR../T

4. Again, search for any folder beginning with “com.apple.appstore” and remove it.

Run a permissions fix on your hard drive

The App Store and software update routines require access to your file system for special system user accounts such as “_softwareupdate.” If your Mac’s permissions routines prevent these and other accounts from accessing necessary resources, then the update process may fail. There are many permissions combinations that will permit appropriate access for these resources; however, if you run Apple’s Permissions Fix routine, then the system will be set up with permissions that ensure proper access. This routine can be done at any time by opening Disk Utility, selecting your boot volume, and then clicking “Fix Permissions” in the First Aid tab.