How do I pipe the entire buffer through an external shell command and replace its contents with the output?

Explanation

The ! filter command in Vim sends a range of lines to an external program as standard input, then replaces those lines with the program's standard output. Using % as the range selects the entire file, making :%!{command} a one-shot way to transform the whole buffer using any shell tool.

How it works

• % — the range covering all lines (equivalent to 1,$)
• ! — the filter operator: pipe range through an external command
• {command} — any shell command that reads from stdin and writes to stdout
• The buffer contents are replaced with the command's output
• Undo with u restores the original content

Example

Sort all lines alphabetically:

:%!sort

Format a JSON file with jq:

:%!jq .

Remove duplicate lines:

:%!sort -u

Base64-encode the buffer:

:%!base64

Tips

• Apply to a range instead of the whole file: :'<,'>!sort sorts only the visually selected lines
• Combine with a line address for a single line: :.!date replaces the current line with the current date
• If the external command fails or produces no output, Vim restores the original lines and shows the error
• The filter approach lets you bring any CLI tool (awk, sed, python, jq, xmllint…) into your editing workflow without leaving Vim