How do I pipe visually selected lines through an external shell command and replace them with the output?

Explanation

Pressing ! while a visual selection is active drops to the command line with :'<,'>! pre-filled. You type a shell command, press <CR>, and Vim pipes the selected lines to the command's stdin—replacing the selection in the buffer with stdout. Any Unix filter (sort, uniq, column, awk, sed, python3 -) can be applied directly to buffer text without leaving Vim.

How it works

1. Visually select one or more lines (V for linewise, <C-v> for block)
2. Press ! — Vim enters the command line with :'<,'>!
3. Type the external command and press <CR>
4. Vim pipes the selection to stdin and replaces it with stdout

The original content is overwritten; use u to undo.

Example

Given these unsorted lines selected with Vj:

banana
apple
cherry

Type !sort<CR>:

apple
banana
cherry

Or align a block of space-delimited columns by selecting them and running !column -t:

name   age  city
alice  30   NY
bob    25   LA

Tips

• Chain commands with pipes: !sort | uniq -c | sort -rn<CR>
• ! in normal mode (without a visual selection) uses a motion: !ip sort<CR> filters the inner paragraph
• !!{cmd}<CR> is the shorthand for filtering only the current line
• The change is a single undoable action — u restores the original lines