Vim can easily execute a shell command with the !. But you can just as easily insert the output of that command into your document.

Simply use :.! like so, where command is whatever you want to run in your shell:

:.!command

For example, try running the following from normal mode:

:.!cal

The line where your cursor was will be replaced with the output of the unix cal command like so:

     June 2017
Su Mo Tu We Th Fr Sa
             1  2  3
 4  5  6  7  8  9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30

If you’d rather insert the output into a new line below your cursor, Vim can do that, too:

:r!