surshar / claude-code
Claude Code is an agentic coding tool that lives in your terminal, understands your codebase, and helps you code faster by executing routine tasks, explaining complex code, and handling git workflows - all through natural language commands.
Built by Anthropic · github.com/anthropics
Example Hook
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| 1 | +#!/usr/bin/env python3 | |
| 2 | +""" | |
| 3 | +Claude Code Hook: Bash Command Validator | |
| 4 | +========================================= | |
| 5 | +This hook runs as a PreToolUse hook for the Bash tool. | |
| 6 | +It validates bash commands against a set of rules before execution. | |
| 7 | +In this case it changes grep calls to using rg. | |
| 8 | + | |
| 9 | +Read more about hooks here: https://docs.anthropic.com/en/docs/claude-code/hooks | |
| 10 | + | |
| 11 | +Make sure to change your path to your actual script. | |
| 12 | + | |
| 13 | +{ | |
| 14 | + "hooks": { | |
| 15 | + "PreToolUse": [ | |
| 16 | + { | |
| 17 | + "matcher": "Bash", | |
| 18 | + "hooks": [ | |
| 19 | + { | |
| 20 | + "type": "command", | |
| 21 | + "command": "python3 /path/to/claude-code/examples/hooks/bash_command_validator_example.py" | |
| 22 | + } | |
| 23 | + ] | |
| 24 | + } | |
| 25 | + ] | |
| 26 | + } | |
| 27 | +} | |
| 28 | + | |
| 29 | +""" | |
| 30 | + | |
| 31 | +import json | |
| 32 | +import re | |
| 33 | +import sys | |
| 34 | + | |
| 35 | +# Define validation rules as a list of (regex pattern, message) tuples | |
| 36 | +_VALIDATION_RULES = [ | |
| 37 | + ( | |
| 38 | + r"^grep\b(?!.*\|)", | |
| 39 | + "Use 'rg' (ripgrep) instead of 'grep' for better performance and features", | |
| 40 | + ), | |
| 41 | + ( | |
| 42 | + r"^find\s+\S+\s+-name\b", | |
| 43 | + "Use 'rg --files | rg pattern' or 'rg --files -g pattern' instead of 'find -name' for better performance", | |
| 44 | + ), | |
| 45 | +] | |
| 46 | + | |
| 47 | + | |
| 48 | +def _validate_command(command: str) -> list[str]: | |
| 49 | + issues = [] | |
| 50 | + for pattern, message in _VALIDATION_RULES: | |
| 51 | + if re.search(pattern, command): | |
| 52 | + issues.append(message) | |
| 53 | + return issues | |
| 54 | + | |
| 55 | + | |
| 56 | +def main(): | |
| 57 | + try: | |
| 58 | + input_data = json.load(sys.stdin) | |
| 59 | + except json.JSONDecodeError as e: | |
| 60 | + print(f"Error: Invalid JSON input: {e}", file=sys.stderr) | |
| 61 | + # Exit code 1 shows stderr to the user but not to Claude | |
| 62 | + sys.exit(1) | |
| 63 | + | |
| 64 | + tool_name = input_data.get("tool_name", "") | |
| 65 | + if tool_name != "Bash": | |
| 66 | + sys.exit(0) | |
| 67 | + | |
| 68 | + tool_input = input_data.get("tool_input", {}) | |
| 69 | + command = tool_input.get("command", "") | |
| 70 | + | |
| 71 | + if not command: | |
| 72 | + sys.exit(0) | |
| 73 | + | |
| 74 | + issues = _validate_command(command) | |
| 75 | + if issues: | |
| 76 | + for message in issues: | |
| 77 | + print(f"• {message}", file=sys.stderr) | |
| 78 | + # Exit code 2 blocks tool call and shows stderr to Claude | |
| 79 | + sys.exit(2) | |
| 80 | + | |
| 81 | + | |
| 82 | +if __name__ == "__main__": | |
| 83 | + main() |