How do I search for 'bar' that is not preceded by 'foo'?

Explanation

Vim regex supports zero-width assertions, so you can match text based on context without consuming the context itself. Negative look-behind is useful when a token is valid almost everywhere, but should be ignored after one specific prefix. This gives you safer navigation and cleaner substitutions in noisy code or logs.

How it works

/foo\@<!bar

• foo is the prefix you want to reject
• \@<! is Vim's negative look-behind atom
• bar is the text you actually want to match

The engine checks the prefix position and only matches bar when foo is not immediately before it. Because the assertion is zero-width, only bar is selected.

Example

Input
foobar
xxbar
bar
myfoobar

Pattern
/foo\@<!bar

Matches
xxbar
bar

Non-matches
foobar
myfoobar

Tips

• Combine this with :vimgrep or :global when you need context-aware filtering
• Keep it explicit before optimizing with very-magic syntax like \v
• If you need more complex context rules, build and test the pattern incrementally