How do I run a substitution or command on every line in the quickfix list?

Explanation

:cdo {cmd} executes {cmd} on each entry in the quickfix list — one by one, jumping to each location in turn. This is the surgical way to apply a change to exactly the files and lines that a previous search or compile step identified, rather than a blanket :bufdo across all open buffers.

How it works

• :cdo {cmd} — run {cmd} on every quickfix entry (each matching line)
• :cfdo {cmd} — run {cmd} once per file that appears in the quickfix list (not per line)
• After running :cdo, use :cfdo update or :wa to save the changed files

A typical workflow using :vimgrep + :cdo:

:vimgrep /oldFunction/ **/*.js
:cdo s/oldFunction/newFunction/g | update

Example

Suppose :vimgrep /TODO/ **/*.py finds 12 occurrences across 5 files. To prepend FIXME: to each TODO comment:

:cdo s/TODO/FIXME: TODO/
:cfdo update

This visits each of the 12 lines and runs the substitution, then saves each affected file exactly once with :cfdo update.

Tips

• Combine with :grep or any tool that populates the quickfix list (e.g., ripgrep via :set grepprg=rg\ --vimgrep)
• Use :cdo norm @a to replay a macro on every quickfix entry
• :ldo and :lfdo are the location-list equivalents if you prefer per-window lists