Hook Creator

Create Claude Code hooks that execute shell commands at specific lifecycle events.

Hook Creation Workflow

• Identify the use case - Determine what the hook should accomplish

• Select the appropriate event - Choose from available hook events (see references/hook-events.md)

• Design the hook command - Write shell command that processes JSON input from stdin

• Configure the matcher - Set tool/event filter (use * for all, or specific tool names like Bash , Edit|Write )

• Choose storage location - User settings (~/.claude/settings.json ) or project (.claude/settings.json )

• Test the hook - Verify behavior with a simple test case

Hook Configuration Structure

{ "hooks": { "<EventName>": [ { "matcher": "<ToolPattern>", "hooks": [ { "type": "command", "command": "<shell-command>" } ] } ] } }

Common Patterns

Reading Input Data

Hooks receive JSON via stdin. Use jq to extract fields:

Extract tool input field

jq -r '.tool_input.file_path'

Extract with fallback

jq -r '.tool_input.description // "No description"'

Conditional processing

jq -r 'if .tool_input.file_path then .tool_input.file_path else empty end'

Exit Codes for PreToolUse

• 0

• Allow the tool to proceed

• 2

• Block the tool and provide feedback to Claude

Matcher Patterns

• Match all tools

• Bash

• Match only Bash tool

• Edit|Write

• Match Edit or Write tools

• Read

• Match Read tool

Quick Examples

Log all bash commands:

jq -r '"(.tool_input.command)"' >> ~/.claude/bash-log.txt

Auto-format TypeScript after edit:

jq -r '.tool_input.file_path' | { read f; [[ "$f" == *.ts ]] && npx prettier --write "$f"; }

Block edits to .env files:

python3 -c "import json,sys; p=json.load(sys.stdin).get('tool_input',{}).get('file_path',''); sys.exit(2 if '.env' in p else 0)"

Resources

• Hook Events Reference: See references/hook-events.md for detailed event documentation with input/output schemas

• Example Configurations: See references/examples.md for complete, tested hook configurations