On the Mac OS X, Terminal app users can use whatis and locate commands to improve their search experience in the terminal similar to Spotlight. whatis : whatis command gives us the short description about the system commands. To display short description whatis uses its "whatis" database. whatis database is set of database files containing short descriptions of system commands which are commonly used in command line , such as in Terminal app. Mac OS X periodically updates the whatis database on a weekly bases if enabled in periodic.conf file. If whatis database is not built then we can build it with following command $ sudo /usr/libexec/makewhatis or $ sudo periodic weekly When we run the whatis command, the output will be as : $ whatis sys...