How do I execute a macro on each quickfix match and write files only when changed?

Explanation

When you already have a precise quickfix list, :cdo is one of the safest ways to run a macro only where it matters. :cdo normal! @a | update executes macro register a at each quickfix entry, then writes the file only if it changed. This avoids blanket :argdo edits across unrelated files and gives you tight scope control for large refactors.

How it works

• :cdo iterates over quickfix entries (not every line in every file)
• normal! @a runs macro a without custom mapping interference
• | update writes the current buffer only when modified

This pairing is powerful because quickfix defines where to edit, and the macro defines what to edit. You can build the list with :vimgrep, :grep, or LSP diagnostics, then apply the same structural fix consistently.

Example

Imagine quickfix contains matches for a legacy API call across many files.

foo_old(arg1)
foo_old(arg2)
foo_old(arg3)

Record macro a once on a representative line to transform to foo_new(...), then run:

:cdo normal! @a | update

Each quickfix hit gets the same edit, and only changed files are saved.

Tips

• Dry-run first with :copen and inspect entries before executing
• Prefer normal! over normal to avoid user mappings affecting macro behavior
• If you need confirmation per location, use a substitution command with c flag instead of a macro
• For window-local lists, use the parallel pattern :ldo ...