How do I pipe the contents of my current buffer as input to a shell command in Vim?

Explanation

The :w !cmd command sends the buffer's contents as standard input to an external command without modifying the buffer. This is fundamentally different from :%!cmd, which replaces the buffer with the command's output. Use :w !cmd when you want to pass your text to a tool for side-effect purposes — copying to the clipboard, counting words, validating syntax — while keeping the buffer intact.

How it works

• :w without a filename normally writes to disk; with !cmd, it pipes to a process instead
• The entire buffer is sent to cmd's stdin
• The buffer is not modified — the command's output is not inserted
• You can restrict the range: :'<,'>w !cmd sends only the visually selected lines

Example

Count the lines and words in the current buffer:

:w !wc -l

Copy the buffer to the macOS clipboard:

:w !pbcopy

Run only the selected lines as a Python script:

:'<,'>w !python3

Tips

• To capture the output into the buffer, use :r !cmd (read) or :%!cmd (filter) instead
• On Linux/WSL, use :w !xclip -selection clipboard or :w !xsel --clipboard --input for clipboard integration
• Combine with a range: :1,10w !sort sends lines 1–10 to sort (output appears below the command line, buffer unchanged)
• The command runs in a shell, so you can use pipes: :w !tr '[:upper:]' '[:lower:]' | wc -c