Select your block of text, then type these keys :w !sh
The whole thing should look like:
:'<,'>w !sh
That’s it. Only took me 8 years to learn that one : )
note: typing : after selecting text produces :'<,’> a range indicating selection start and end.
Update 2016: This is really just one use of the generic:
'<,'>w !cli_command
Which basically lets you “send” arbitrary parts of your file to external commands and see the results in a temporary vi window without altering your buffer. Other useful examples would be:
'<,'>w !wc
'<,'>w !to_file my_file
I honestly find it more useful to alter the current buffer. This variety is simply:
'<,'>!wc
'<,'>!to_file my_file