Char-Index String Manipulation

Precise index-based string operations. Use when you need exact character positioning for test generation, parsing, or LLM response extraction.

Operations (12 tools)

All via python ${CLAUDE_SKILL_DIR}/scripts/char_ops.py <command> [options]. Returns JSON.

Finding (4)

• find-nth-char: Find nth occurrence of char → {"index": N}
• find-all-chars: All positions of char → {"indices": [...]}
• find-nth-substring: Find nth occurrence of substring → {"index": N}
• find-all-substrings: All positions of substring → {"indices": [...]}

Splitting & Extraction (4)

• split-at: Split at indices → {"parts": [...]}
• extract: Substring by range → {"substring": "...", "length": N}
• extract-between: Content between markers → {"content": "...", "content_start": N, ...}
• extract-batch: Multiple ranges → {"results": [{...}, ...]}

Modification (3)

• insert: Insert at index → {"result": "..."}
• delete: Delete range [start, end) → {"result": "..."}
• replace: Replace range with text → {"result": "..."}

Utilities (1)

• count: Character statistics → {"total": N, "letters": N, "digits": N, ...}

Quick Reference

Task	Command
Find 3rd 'l'	find-nth-char --text "hello world" --char "l" --n 3
All 'l' positions	find-all-chars --text "hello world" --char "l"
Split at 2,5,8	split-at --text "hello world" --indices "2,5,8"
Extract chars 0-5	extract --text "hello world" --start 0 --end 5
Between markers	extract-between --text "a[b]c" --start-marker "[" --end-marker "]"
Insert comma	insert --text "hello world" --index 5 --insertion ","
Delete range	delete --text "hello world" --start 5 --end 11
Replace range	replace --text "hello world" --start 6 --end 11 --replacement "Python"
Count chars	count --text "hello world"

Usage Patterns

Basic:

python ${CLAUDE_SKILL_DIR}/scripts/char_ops.py find-nth-char \
  --text "hello world" --char "l" --n 3
# {"index": 9}

Chain with jq:

INDEX=$(python ${CLAUDE_SKILL_DIR}/scripts/char_ops.py find-nth-char \
  --text "$TEXT" --char "x" --n 1 | jq -r '.index')

Batch operations:

python ${CLAUDE_SKILL_DIR}/scripts/char_ops.py extract-batch \
  --text "hello world" \
  --ranges '[{"start":0,"end":5},{"start":6,"end":11}]'

Key Points

• 0-indexed: All positions start from 0
• 1-based occurrence: find-nth-* uses --n 1 for first occurrence
• Negative indices: -1 = last char, -5 = 5th from end
• Returns -1: When char/substring not found
• Range format: [start, end) - start inclusive, end exclusive
• Unicode safe: Each Unicode character = 1 position
• Overlaps included: find-all-* finds overlapping matches

More Info

• Practical examples: examples.md
• Command help: python ${CLAUDE_SKILL_DIR}/scripts/char_ops.py --help