How to run Unix commands from within Vim?

Go to command mode Esc, then run . Anything run from the prompt starting with a bang will be run as a unix shell command. You'll be shown the output and allowed to hit a key to get back to your work in vim. If you have text selected in visual mode and want to send it TO a command as STDIN, hit and enter your command. The results of the command will replace the text you have selected.