| name | regex-builder |
|---|---|
| description | Build, test, and explain regular expressions against sample text or files using CLI tools (rg, python) and specific regex flavors. Use when asked to craft, debug, or validate regexes or search patterns. |
Regex builder
Goal
Produce a correct, testable regex with rationale and runnable verification.
Inputs to confirm (ask if missing)
- Target regex flavor/engine (PCRE, Python, JavaScript, .NET, RE2, etc.).
- Example matches and non-matches (at least 3 each when possible).
- Scope: single-line vs multi-line; file types/paths.
- Output needs: capture groups, named groups, replacement template.
Workflow
1) Gather samples
- Ask for sample text or identify files.
- If files exist, locate with rg --files and preview with rg -n.
2) Choose tool
- Prefer rg for quick match checks; use rg -P for PCRE features.
- Use Python for detailed group inspection when needed.
3) Build incrementally
- Start with a minimal literal anchor; expand piece by piece.
- Add anchors/boundaries; handle whitespace and separators explicitly.
4) Validate
- Show a command to test against samples.
- Confirm no false positives by testing non-matches.
5) Deliver
- Provide final regex, flags, and explanation.
- Include a test command and expected match summary.
- Note any tradeoffs/backtracking risks.
CLI snippets (use as needed)
- Ripgrep check:
rg -n "<regex>" path\\to\\filerg -n -P "<regex>" path\\to\\file- Python quick test (adjust quoting for the shell):
python -c "import re,sys;pat=re.compile(r'<regex>');data=sys.stdin.read();print([m.group(0) for m in pat.finditer(data)])" < path\\to\\file
Deliverables
- Regex + flags and any capture group map.
- Test command(s) and summary of matches/non-matches.
- Short explanation of the approach and known limitations.