Turns out it can, and so I iterated on the idea, building it into a full CLI tool. Recently I wanted to improve it by adding relevance of tools like Sourcegraph or Zoekt but again without adding an index.
cs uses scc https://github.com/boyter/scc to understand the structure of the file on the fly. As such it can filter searches to code, comments or strings. It also applies a weighted BM25 algorithm where matches in actual code rank higher than matches in comments (by default).
I also added a complexity gravity weight using the cyclomatic complexity output from scc as it scans. So if you're searching for a function, the implementation should rank higher than the interface.
cs "authenticate" --gravity=brain # Find the complex implementation, not the interface
cs "FIXME OR TODO OR HACK" --only-comments # Search only in comments, not code or strings
cs "error" --only-strings # Find where error messages are defined
cs "handleRequest" --only-usages # Find every call site, skip the definition
Since it's doing analysis and complexity math on the fly, it's slower than any grep. However, on an M1 Mac, it can scan and rank the entire 40M+ line Linux kernel in ~6 seconds.
Live demo (running over its own source code in HTTP mode): https://codespelunker.boyter.org/ GitHub: https://github.com/boyter/cs