While in vim, you may want to run an external command and use the output. One way is to do the following.

:new | r !ls

The !ls runs the external command ls. The r reads the output of the command and places it under the cursor. The new creates a new buffer in a split window, and places the cursor there.

The result is a split window containing the output of the external shell command.

This was done using Ubuntu 16.04 LTS and Vim 7.4.