How do I create a macro that only acts on lines matching a search pattern?

Explanation

By starting a macro with a search command, the macro becomes conditional — it jumps to the next match before acting, and terminates when no more matches are found. This creates a targeted macro that skips non-matching lines automatically.

How it works

• /pattern<CR> — jump to next match (fails when no more matches exist)
• Perform the desired action on that match
• @a — recurse to find and process the next match
• The macro chain stops when the search wraps around or finds no match

Example

" Delete all lines containing 'DEBUG'
qaq
qa/DEBUG<CR>dd@aq
@a

" Change all 'var' to 'let'
qaq
qa/var<CR>cwlet<Esc>@aq
@a

Before:
const x = 1;
var y = 2;
const z = 3;
var w = 4;

After running the var→let macro:
const x = 1;
let y = 2;
const z = 3;
let w = 4;

Tips

• For simple cases, :g/pattern/d or :%s/old/new/g are more direct
• Macros shine when the transformation is complex (multiple steps per match)
• Use n instead of /pattern<CR> if the search is already set
• Set nowrapscan to prevent the search from wrapping: :set nowrapscan