Most of the Operating Systems now a days offers search within it, Linux is modern desktop which offers many more features than any other Operating System. Ubuntu Unity has its Dash, Gnome Shell desktop also has integrated search, Whisper can be used in Xfce, KDE also offers search from menu, Mate and Cinnamon desktops already have this feature. Mac yosemite introduced new spotlight, it is an productivity feature available in Mac OS. But there are always some Linux users who bring new stuff to Linux and make it better than any other OS.
Here comes Mutate alternative to OS-X spotlight created by Wei Qiang, it offers pretty much same features like Spotlight or maybe better than Spotlight. It is a selection-based search system, which creates an index of all items and files on the system. It is designed to allow the user to quickly locate a wide variety of items on the computer, including documents, pictures, music, applications, and System Preferences. It also can run some Linux terminal commands, open URLs in web browser, translate from one language to other, and also allows you to shutdown/logout/restart computer.
Open URLs in browser
Google Search right from Mutate
Kill any running Process/Application
Find files (Can search files using extensions)
Type 'preference' to open Mutate Preferences
Set Custom hotkey or add new item from preferences
To install Mutate in Ubuntu 15.04/14.10/14.04/Linux Mint 17.1/17 open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal: