This can be achieved with two packages:

Overall, smart-mode-line is more powerful than powerline (pardon the pun), in the sense that it offers more features to control the mode-line's behaviour and more customizability in the appearance. The Readme has a great list of features, but in short it offers width-control, string replacement in the file path, hiding of the minor modes, among other things.

If all you want is to achieve the screenshot, powerline is the best choice.

is the best choice. If you want a suite of other features combined with that, give smart-mode-line a try.

Since powerline has been very well explained on another answer, I'll focus on how you can achieve that appearance with smart-mode-line.

First Install

You can install smart-mode-line from Melpa, Melpa-Stable, or download it manually. Assuming you decide to use the package manager, just do

M-x package-install RET smart-mode-line

Once you turn it on with M-x sml/setup , your mode-line should look similar to one of these two.



Powerline Theme

smart-mode-line has several themes built-in, the one that achieves the requested appearance is provided separately in the themes/ directory. Note that this theme is still in beta, so customizing it might not work perfectly just yet.

Install the theme from Melpa

M-x package-install RET smart-mode-line-powerline-theme

If you want to install it manually, it's here, but you'll also need to install powerline.

Finally you can turn on the theme with M-x sml/apply-theme RET powerline . And your mode-line should then look like this.



As you can see, the order of elements is not quite the same, but the overall appearance is there.

To use this theme every-time, add the following to your init file. You can also customize any of the powerline configuration variables, and they should have the same effect here.