Regex Builder

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\\file
  • rg -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.

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