Mac OS X Mavericks has an option which is available as part of System Preferences that enables automatic app updates on the system.
Launching App Store Preferences
Step 1: Click the Apple icon and select System Preferences from the menu list.
Step 2: In the System Preferences window, click the App Store option.
This would display the following App Store Preferences screen.
Step 3: You can enable automatic app updates on Mac OS X by marking the checkbox with caption as “Install app updates”.
By enabling this option, all software updates related with Mac System and Apps except third party softwares will be automatically updated.
Turn off automatic check for updates
If for some reason you do not want the system to automatically check for updates then you can un mark the check box with label as “Automatic check for updates”. And you can manually install by clicking the Show Updates.
Apps purchased on other Mac
App Store preferences also provides option to automatically install apps purchased on other Macs. You can enable this feature by marking the checkbox with caption as “Automatically download apps purchased on other Macs”. This is quite useful when you have more than one Mac and want to keep the system updated with downloads done on other Macs.